Aqueous base paints containing cross-linked polyurethane binders and a special solvent composition

ABSTRACT

Provided herein is a pigmented aqueous basecoat material including an aqueous polyurethane-polyurea dispersion (PD) having polyurethane-polyurea particles present in the dispersion, an average particle size (volume average) of 40 to 2000 nm, and a gel fraction of at least 50 wt %. The polyurethane-polyurea particles, in each case in reacted form, include: at least one polyurethane prepolymer containing isocyanate groups and including anionic groups and/or groups which can be converted into anionic groups, and at least one polyamine comprising two primary amino groups and one or two secondary amino groups. The aqueous basecoat material includes a specific solvent composition. Also provided herein is a method of using basecoat materials including the dispersion (PD) and multicoat paint systems produced using the basecoat materials.

The present invention relates to a pigmented aqueous basecoat materialcomprising a polyurethane-polyurea dispersion and also a specificsolvent composition. The present invention also relates to the use of anaqueous basecoat material comprising a polyurethane-polyurea dispersionand the specific solvent composition for improving the applicationsproperties of basecoat materials and coatings produced using thebasecoat material. Especially in connection with the construction ofmulticoat paint systems, the aqueous basecoat material comprising thisdispersion and the specific solvent composition possesses outstandingstorage stability while maintaining good applications properties.

PRIOR ART

Multicoat paint systems on a wide variety of different substrates, asfor example multicoat paint systems on metallic substrates within theautomobile industry, are known. In general, multicoat paint systems ofthis kind comprise, viewed from the metallic substrate outward, anelectrocoat, a layer which has been applied directly to the electrocoatand is usually referred to as the primer-surfacer coat, at least onecoat which comprises color pigments and/or effect pigments and isgenerally referred to as the basecoat, and a clearcoat. The basiccompositions and functions of these layers and of the coatingcompositions needed to form these layers, i.e. electrocoat materials,so-called primer-surfacers, coating compositions which comprise colorpigments and/or effect pigments and are known as basecoat materials, andclearcoat materials, are known. Accordingly, for example, theelectrocoat serves basically to protect the substrate from corrosion.The so-called primer-surfacer coat serves principally for protectionfrom mechanical stress, for example stone-chipping, and additionally tolevel out unevenness in the substrate. The next coat, referred to as thebasecoat, is principally responsible for the creation of estheticproperties such as color and/or effects such as flop, while theclearcoat which then follows serves particularly to impart scratchresistance and the gloss of the multicoat paint system.

Multicoat paint systems of this kind, and also methods for producingthem, are described in, for example, DE 199 48 004 A1, page 17, line 37,to page 19, line 22, or else in DE 100 43 405 C1, column 3, paragraph[0018], and column 8, paragraph [0052], to column 9, paragraph [0057],in conjunction with column 6, paragraph [0039] to column 8, paragraph[0050].

The known multicoat paint systems are already able to meet many of theapplications properties required by the automobile industry. In therecent past, progress has also been made in terms of the environmentalprofile of such paint systems, especially through the increased use ofaqueous coating materials, of which aqueous basecoat materials are anexample.

A problem which nevertheless occurs again and again in connection withthe production of multicoat paint systems lies in the formation ofunwanted inclusions of air, of solvents and/or of moisture, which maybecome apparent in the form of bubbles beneath the surface of theoverall paint system, and may burst open in the course of final curing.The holes that are formed in the paint system as a result, also calledpinholes and pops, lead to a disadvantageous visual appearance. Theamounts of organic solvents and/or water involved, and also the quantityof air introduced as a result of the application procedure, are toogreat to allow the overall amount to escape from the multicoat paintsystem in the course of curing, without giving rise to defects.

In general the robustness with respect to the development of runs, pops,and pinholes is collated under the heading of applications properties.Running is understood as the sagging of coating materials which havebeen applied, but which are not yet fully dried or cured, on vertical orinclined surfaces. This sagging gives rise in general to an unattractiveand uneven appearance in the coating that results after curing.

The environmental profile of multicoat paint systems is also still inneed of improvement. A contribution in this respect has, indeed, alreadybeen achieved through the replacement of a significant fraction oforganic solvents by water in aqueous paints. A significant improvement,nevertheless, would be achievable by an increase in the solids contentof such paints. However, especially in aqueous basecoat materials, whichcomprise color pigments and/or effect pigments, the storage stability isdetrimentally affected as the solids content is increased. The storagestablility here describes for example the time-dependent sedimentationbehavior of pigments of the paint. The storage stability of coatingmaterials or paints, examples being aqueous basecoat materials, whichcomprise polymer dispersions as binders, for example, is influenced byfactors including the rate of sedimentation as a function of the size ofthe particles from the dispersions, and the effect of the solvent on thestabilization of those particles, and also the effect on the viscosity.The storage stability can be described by means of viscositymeasurements in the liquid state over time.

The level of the solids content likewise influences other rheologicalproperties, such as a pronounced structural viscosity. It is oftenachieved through the use of inorganic phyllosilicates. Although the useof such silicates can result in very good properties of structuralviscosity, the coating materials in question are in need of improvementwith regard to their solids content.

The prior art describes a wide variety of specific polymers, their usein coating materials, and also their advantageous effect on variousapplications properties of paint systems and coatings.

DE 197 19 924 A1 describes a process for preparing a storage-stabledispersion of polyurethanes containing amino groups, the preparation ofwhich involves reaction of polyurethane prepolymers containingisocyanate groups with specific polyamines that have no primary aminogroups, and involves dispersion in water before or after the reaction.One possible area of application is the provision of coating materials.

DE 31 37 748 A1 describes storage-stable aqueous dispersions ofpolyurethane-polyureas produced, again, by reaction of a polyurethaneprepolymer containing isocyanate groups with a specific polyamine. Onepossible area of application is the provision of coatings on metallicsubstrates.

WO 2014/007915 A1 discloses a method for producing a multicoatautomobile finish, using an aqueous basecoat material which comprises anaqueous dispersion of a polyurethane-polyurea resin. The use of thebasecoat material produces positive effects on the optical properties,in particular a minimizing of gel specks.

WO 2012/160053 A1 describes hydrophilic layer assemblies for medicalinstruments, with aqueous dispersions of polyurethane-polyurea resinsbeing among the components used in producing the assembly.

Likewise described is the use of microgels, or dispersions of suchmicrogels, in various coating materials, in order thereby to optimizedifferent applications properties of coating systems. A microgeldispersion, as is known, is a polymer dispersion in which, on the onehand, the polymer is present in the form of comparatively smallparticles, having particle sizes of 0.02 to 10 micrometers, for example(“micro”-gel). On the other hand, however, the polymer particles are atleast partly intramolecularly crosslinked; the internal structure,therefore, equates to that of a typical polymeric network. Because ofthe molecular nature, however, these particles are in solution insuitable organic solvents; macroscopic networks, by contrast, wouldmerely swell. The physical properties of such systems with crosslinkedparticles in this order of magnitude, often also called mesoscopic inthe literature, lie between the properties of macroscopic structures andmicroscopic structures of molecular liquids (see, for example, G. Nimtz,P. Marquardt, D. Stauffer, W. Weiss, Science 1988, 242, 1671). Microgelsare described with more precision later on below.

DE 35 13 248 A1 describes a dispersion of polymeric micropolymerparticles, the dispersion medium being a liquid hydrocarbon. Preparationinvolves the reaction of a prepolymer containing isocyanate groups witha polyamine such as diethylenetriamine. An advantage cited is theimprovement in the resistance to sagging of coatings which comprise themicropolymer particles.

U.S. Pat. No. 4,408,008 describes stable, colloidal aqueous dispersionsof crosslinked urea-urethanes whose preparation involves reacting aprepolymer—which is in dispersion in aqueous solution, which containsisocyanate groups, and which comprises hydrophilic ethylene oxideunits—with polyfunctional amine chain extenders. The films producedtherefrom possess, for example, good hardness and tensile strength.

EP 1 736 246 A1 describes aqueous basecoat materials for application inthe area of automobile finishing, comprising a polyurethane-urea resinwhich is in dispersion in water and which possesses a crosslinkedfraction of 20% to 95%. This aqueous crosslinked resin is prepared in atwo-stage process, by preparation of a polyurethane prepolymercontaining isocyanate groups, and subsequent reaction of this prepolymerwith polyamines. The prepolymer, in a solution in acetone with a solidscontent of about 80%, is dispersed in water, and then reacted with thepolyamine. The use of this crosslinked resin results in advantageousoptical properties on the part of multicoat paint systems.

DE 102 38 349 A1 describes polyurethane microgels in water, with onemicrogel explicitly produced having a crosslinked gel fraction of 60%.The microgels are used in waterborne basecoat materials, where they leadto advantageous rheological properties. Furthermore, through the use ofthe waterborne basecoat materials in the production of multicoat paintsystems, advantages are achieved in respect of decorative properties andadhesion properties.

As a result of the highly promising applications properties of microgeldispersions, particularly aqueous microgel dispersions, this class ofpolymer dispersions is seen as particularly highly promising for use inaqueous coating materials.

It should nevertheless be noted that such microgel dispersions, ordispersions of polymers having a crosslinked gel fraction as describedabove, must be formed in such a way that not only do the statedadvantageous properties result, but also, furthermore, no adverseeffects arise on other important properties of aqueous coatingmaterials. Thus, for example, it is difficult to provide microgeldispersions with polymer particles of a defined particle size that onthe one hand have the crosslinked character described, but on the otherhand permit an appropriate storage stability. The storage stability, orits sedimentation behavior, is determined in this case by the size ofthe particles and their stabilization in the dispersion or in the paintor the coating material. As is known, dispersions having comparativelylarger particles, in the range of, for example, greater than 2micrometers (average particle size), possess increased sedimentationbehavior and hence an impaired storage stability. Also inadequatelydealt with in the prior art is the effect of the solvents used in thecoating material on the stabilization of these particles and hence theeffect of the solvents on the sedimentation behavior or on the storagestability of the coating material.

Problem

The problem for the present invention, accordingly, was first of all toprovide aqueous coating materials, more particularly basecoat materialscomprising an aqueous polymer dispersion which allow excellent storagestability of these basecoat materials to be established, with retentionof good applications properties, through deliberate selection of thesolvents used and their composition. Ultimately, therefore, in paintsystems, especially multicoat paint systems, produced using astorage-stable basecoat material of this kind, the good applicationsproperties ought to be retained, more particularly a good pinholingbehavior, here further, in particular, a reduced number of pinholes orpinholing limit, and good running stability.

The coating materials formulated with the polymer dispersion oughttherefore to be storage-stable as a result of appropriate selection ofthe solvent composition used, and at the same time ought likewise to bepreparable in an environmentally advantageous way, in particular with ahigh solids content, with good applications properties being retained oreven improved.

Technical Solution

It has been found that the problems identified can be solved by means ofa new pigmented aqueous basecoat material comprising an aqueouspolyurethane-polyurea dispersion (PD) having polyurethane-polyureaparticles, present in the dispersion, having an average particle size(volume average) of 40 to 2000 nm, and having a gel fraction of at least50 wt %, the polyurethane-polyurea particles, in each case in reactedform, comprising

(Z.1.1) at least one polyurethane prepolymer containing isocyanategroups and comprising anionic groups and/or groups which can beconverted into anionic groups, and also

(Z.1.2) at least one polyamine comprising two primary amino groups andone or two secondary amino groups,

wherein

the aqueous basecoat material, based on the total amount of solvents (L)present in the basecoat material, contains in total less than 9 wt % ofsolvents selected from the group consisting of solvents (L1) having aHLB of between 5 and 15 and a water solubility of >1.5 wt % at 20° C.,

the HLB of a solvent (L) being defined as follows:

HLB(L)=20*(1−M(lipophilic fraction of (L))/M(L)),

the lipophilic fraction of a solvent (L) being made up of the followingcarbon-containing groups:

every group CH_(n) with n=1 to 3, provided that the group

(i) is not in alpha position to OH, NH₂, CO₂H,

(ii) is not in ethylene oxide units located in an ethylene oxide chainhaving a terminal OH group, and/or

(iii) is not in a cyclic molecule or molecular moiety in alpha positionto a bridging functional group selected from —O—, NH—.

The new aqueous dispersion is also referred to below as aqueous basecoatmaterial of the invention. Preferred embodiments of the aqueous basecoatmaterial of the invention are apparent from the description whichfollows and from the dependent claims.

The present invention likewise provides a method for producing multicoatpaint systems using the pigmented aqueous basecoat material of theinvention, and also the multicoat paint systems producible by means ofsaid method. The present invention further relates to the use of thepigmented aqueous basecoat material of the invention for improving thestorage stability and the applications properties of multicoat paintsystems.

It has emerged that through appropriate selection of specific solventsin particular limits in aqueous basecoat materials comprising thedispersion (PD), it is possible to achieve outstanding storage stabilitywith retention of good applications properties for multicoat paintsystems having been produced using the basecoat materials. Noteworthyabove all are the small change in the high-shear viscosity of thebasecoat material of the invention over a prolonged time period, ameasure of the storage stability, with retention of the goodapplications properties, in particular the good pinholing behavior andalso a good running stability. Moreover, the coating materialsformulated with the dispersion can be produced in an environmentallyadvantageous way, more particularly with a high solids content and/orwith reduction in the amount of specific solvents, with no disadvantagesresulting in the storage stability area or in the area of applicationsproperties.

DESCRIPTION

The present invention provides a pigmented aqueous basecoat material(waterborne basecoat material) comprising at least one, preferablyexactly one, specific polyurethane-polyurea dispersion (PD) and aspecific solvent composition. All preferred embodiments specified lateron below in relation to the dispersion (PD) are of course alsoapplicable in relation to the basecoat material comprising thedispersion (PD).

A basecoat material is a color-imparting intermediate coating materialthat is used in automotive finishing and general industrial painting.This basecoat material is generally applied to a metallic or plasticssubstrate which has been pretreated with a baked (fully cured)primer-surfacer, or else, occasionally, is applied directly to theplastics substrate or directly to an electrocoated metallic substrate.Substrates used may also include existing paint systems, which mayoptionally require pretreatment as well (by abrading, for example). Toprotect a basecoat film from environmental effects in particular, atleast one additional clearcoat film is generally applied over it. Thisis generally done in a wet-on-wet process—that is, the clearcoatmaterial is applied without the basecoat film being cured. Curing thentakes place, finally, together with the clearcoat.

The basecoat material of the invention comprises at least one,preferably exactly one, specific aqueous polyurethane-polyureadispersion (PD).

The polymer particles present in the dispersion are thereforepolyurethane-polyurea-based. Such polymers are preparable in principleby conventional polyaddition of, for example, polyisocyanates withpolyols and also polyamines. With a view to the dispersion (PD) for usein accordance with the invention and to the polymer particles itcontains, however, there are specific conditions to be observed, whichare elucidated below.

The polyurethane-polyurea particles present in the aqueouspolyurethane-polyurea dispersion (PD) possess a gel fraction of at least50 wt % (for measurement method, see Example section). Moreover, thepolyurethane-polyurea particles present in the dispersion (PD) possessan average particle size (volume average) of 40 to 2000 nanometers (nm)(for measurement method, see Example section).

The dispersions (PD) for use in accordance with the invention,therefore, are microgel dispersions. Indeed, as is known, a microgeldispersion is a polymer dispersion in which on the one hand the polymeris present in the form of comparatively small particles having particlesizes of, for example, 0.02 to 10 micrometers (“micro” gel). On theother hand, however, the polymer particles are at least partlyintramolecularly crosslinked. The latter means that the polymerstructures present within a particle equate to a typical macroscopicnetwork, with three-dimensional network structure. Viewedmacroscopically, however, a microgel dispersion of this kind continuesto be a dispersion of polymer particles in a dispersion medium, waterfor example. While the particles may also in part have crosslinkingbridges to one another (purely from the preparation process, this canhardly be ruled out), the system is nevertheless a dispersion withdiscrete particles included therein that have a measurable averageparticle size. On account of the molecular nature, however, they are insolution in suitable organic solvents, whereas macroscopic networkswould only be swollen.

Because the microgels represent structures which lie between branchedand macroscopically crosslinked systems, they combine, consequently, thecharacteristics of macromolecules with network structure that aresoluble in suitable organic solvents, and insoluble macroscopicnetworks, and so the fraction of the crosslinked polymers can bedetermined, for example, only following isolation of the solid polymer,after removal of water and any organic solvents, and subsequentextraction. The phenomenon utilized here is that whereby the microgelparticles, originally soluble in suitable organic solvents, retain theirinner network structure after isolation, and behave, in the solid, likea macroscopic network. Crosslinking may be verified via theexperimentally accessible gel fraction. The gel fraction is ultimatelythe fraction of the polymer from the dispersion that cannot bemolecularly dispersely dissolved, as an isolated solid, in a solvent. Itis necessary here to rule out a further increase in the gel fractionfrom crosslinking reactions subsequent to the isolation of the polymericsolid. This insoluble fraction corresponds in turn to the fraction ofthe polymer that is present in the dispersion in the form ofintramolecularly crosslinked particles or particle fractions.

In the context of the present invention, it has emerged that only thespecific solvent composition essential to the invention in combinationwith the microgel dispersions has all of the required applicationproperties. Particularly important, therefore, is the combination of thestabilization of the polymer particles contained in the dispersion, saidparticles having fairly low particle sizes with the aid of the solventsused and, nevertheless, a significant crosslinked fraction or gelfraction. Only in this way is it possible to achieve the advantageousproperties, more particularly the good storage stability of the aqueousbasecoat materials while maintaining the good application properties ofmulticoat paint systems.

The polyurethane-polyurea particles present in the aqueouspolyurethane-polyurea dispersion (PD) preferably possess a gel fractionof at least 50 wt %, more preferably of at least 65 wt %, especiallypreferably of at least 80 wt %. The gel fraction may therefore amount toup to 100 wt % or approximately 100 wt %, as for example 99 wt % or 98wt %. In such a case, then, the entire—or almost theentire—polyurethane-polyurea polymer is present in the form ofcrosslinked particles.

The polyurethane-polyurea particles present in the dispersion (PD)preferably possess an average particle size (volume average) of 40 to2000 nm, more preferably of 100 to 1500 nm, more preferably 110 to 500nm, and even more preferably 120 to 300 nm. An especially preferredrange is from 130 to 250 nm.

The polyurethane-polyurea dispersion (PD) obtained is aqueous. Theexpression “aqueous” is known in this context to the skilled person. Itrefers fundamentally to a system which comprises as its dispersionmedium not exclusively or primarily organic solvents (also calledsolvents); instead, it comprises as its dispersion medium a significantfraction of water. Preferred embodiments of the aqueous character,defined on the basis of the maximum amount of organic solvents and/or onthe basis of the amount of water, are described later on below.

The polyurethane-polyurea particles present in the dispersion (PD)comprise, in each case in reacted form, (Z.1.1) at least onepolyurethane prepolymer containing isocyanate groups and comprisinganionic groups and/or groups which can be converted into anionic groups,and also (Z.1.2) at least one polyamine comprising two primary aminogroups and one or two secondary amino groups.

Where it is said in the context of the present invention that polymers,as for example the polyurethane-polyurea particles of the dispersion(PD), comprise certain components in reacted form, this means that theseparticular components are used as starting compounds for the preparationof the polymers in question. Depending on the nature of the startingcompounds, the respective reaction to form the target polymer takesplace according to different mechanisms. Presently, then, in theproduction of polyurethane-polyurea particles or polyurethane-polyureapolymers, components (Z.1.1) and (Z.1.2) are reacted with one another byreaction of the isocyanate groups of (Z.1.1) with the amino groups of(Z.1.2) to form urea bonds. The polymer in that case of course comprisesthe isocyanate groups and amino groups, previously present, in the formof urea groups, in other words in their correspondingly reacted form.Ultimately, nevertheless, the polymer comprises the two components(Z.1.1) and (Z.1.2), since apart from the reacted isocyanate groups andamino groups, the components remain unchanged. Accordingly, for the sakeof clarity, it is stated that the respective polymer comprises thecomponents, in each case in reacted form. The meaning of the expression“the polymer comprises, in reacted form, a component (X)” can thereforebe equated with the meaning of the expression “component (X) was used inthe course of the preparation of the polymer”.

It follows from the above that anionic groups and/or groups which can beconverted into anionic groups are introduced, via the aforementionedpolyurethane prepolymer containing isocyanate groups, into thepolyurethane-polyurea particles.

The polyurethane-polyurea particles consist preferably of the twocomponents (Z.1.1) and (Z.1.2), meaning that they are prepared fromthese two components.

The aqueous dispersion (PD) can be obtained by a specific three-stageprocess, which is preferred. In the context of the description of thisprocess, preferred embodiments of the components (Z.1.1) and (Z.1.2) arealso stated.

In a first step (I) of this process, a specific composition (Z) isprepared.

The composition (Z) comprises at least one, preferably precisely one,specific intermediate (Z.1) which contains isocyanate groups and hasblocked primary amino groups.

The preparation of the intermediate (Z.1) involves the reaction of atleast one polyurethane prepolymer (Z.1.1), containing isocyanate groupsand comprising anionic groups and/or groups which can be converted intoanionic groups, with at least one polyamine (Z.1.2a) derived from apolyamine (Z.1.2), comprising two blocked primary amino groups and oneor two free secondary amino groups.

Polyurethane polymers containing isocyanate groups and comprisinganionic groups and/or groups which can be converted into anionic groupsare known in principle. For the purposes of the present invention,component (Z.1.1) is referred to as prepolymer, for greater ease ofcomprehension. This component is in fact a polymer which can be referredto as a precursor, since it is used as a starting component forpreparing another component, specifically the intermediate (Z.1).

For preparing the polyurethane prepolymers (Z.1.1) which containisocyanate groups and comprise anionic groups and/or groups which can beconverted into anionic groups, it is possible to employ the aliphatic,cycloaliphatic, aliphatic-cycloaliphatic, aromatic, aliphatic-aromaticand/or cycloaliphatic-aromatic polyisocyanates that are known to theskilled person. Diisocyanates are used with preference. Mention may bemade, by way of example, of the following diisocyanates: 1,3- or1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4′- or2,4′-diphenylmethane diisocyanate, 1,4- or 1,5-naphthylene diisocyanate,diisocyanatodiphenyl ether, trimethylene diisocyanate, tetramethylenediisocyanate, ethylethylene diisocyanate, 2,3-dimethylethylenediisocyanate, 1-methyltrimethylene diisocyanate, pentamethylenediisocyanate, 1,3-cyclopentylene diisocyanate, hexamethylenediisocyanate, cyclohexylene diisocyanate, 1,2-cyclohexylenediisocyanate, octamethylene diisocyanate, trimethylhexane diisocyanate,tetramethylhexane diisocyanate, decamethylene diisocyanate,dodecamethylene diisocyanate, tetradecamethylene diisocyanate,isophorone diisocyanate (IPDI), 2-isocyanatopropylcyclohexyl isocyanate,dicyclohexylmethane 2,4′-diisocyanate, dicyclohexylmethane4,4′-diisocyanate, 1,4- or 1,3-bis(isocyanatomethyl)-cyclohexane, 1,4-or 1,3- or 1,2-diisocyanato-cyclohexane, 2,4- or2,6-diisocyanato-1-methylcyclohexane,1-isocyanatomethyl-5-isocyanato-1,3,3-trimethylcyclohexane,2,3-bis(8-isocyanatooctyl)-4-octyl-5-hexylcyclohexene,tetramethylxylylene diisocyanates (TMXDI) such as m-tetramethylxylylenediisocyanate, or mixtures of these polyisocyanates. Also possible, ofcourse, is the use of different dimers and trimers of the stateddiisocyanates, such as uretdiones and isocyanurates. Polyisocyanates ofhigher isocyanate functionality may also be used. Examples thereof aretris(4-isocyanatophenyl)methane, 1,3,4-triisocyanatobenzene,2,4,6-triisocyanato-toluene, 1,3,5-tris(6-isocyanatohexylbiuret),bis(2,5-diisocyanato-4-methylphenyl)methane. The functionality mayoptionally be lowered by reaction with monoalcohols and/or secondaryamines. Preference, however, is given to using diisocyanates, moreparticularly to using aliphatic diisocyanates, such as hexamethylenediisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane4,4′-diisocyanate, 2,4- or 2,6-diisocyanato-1-methylcyclohexane, andm-tetramethylxylylene diisocyanate (m-TMXDI). An isocyanate is termedaliphatic when the isocyanate groups are attached to aliphatic groups;in other words, when there is no aromatic carbon present in alphaposition to an isocyanate group.

The prepolymers (Z.1.1) are prepared by reacting the polyisocyanateswith polyols, more particularly diols, generally with formation ofurethanes.

Examples of suitable polyols are saturated or olefinically unsaturatedpolyester polyols and/or polyether polyols. Polyols used moreparticularly are polyester polyols, especially those having anumber-average molecular weight of 400 to 5000 g/mol (for measurementmethod, see Example section). Such polyester polyols, preferablypolyester diols, may be prepared in a known way by reaction ofcorresponding polycarboxylic acids, preferably dicarboxylic acids,and/or their anhydrides with corresponding polyols, preferably diols, byesterification. It is of course optionally possible in addition, evenproportionally, to use monocarboxylic acids and/or monoalcohols for thepreparation. The polyester diols are preferably saturated, moreparticularly saturated and linear.

Examples of suitable aromatic polycarboxylic acids for preparing suchpolyester polyols, preferably polyester diols, are phthalic acid,isophthalic acid, and terephthalic acid, of which isophthalic acid isadvantageous and is therefore used with preference. Examples of suitablealiphatic polycarboxylic acids are oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, undecanedicarboxylic acid, and dodecanedicarboxylicacid, or else hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid,tricyclodecane-dicarboxylic acid, and tetrahydrophthalic acid. Asdicarboxylic acids it is likewise possible to use dimer fatty acids ordimerized fatty acids, which, as is known, are mixtures prepared bydimerizing unsaturated fatty acids and are available, for example, underthe commercial names Radiacid (from Oleon) or Pripol (from Croda). Inthe context of the present invention, the use of such dimer fatty acidsfor preparing polyester diols is preferred. Polyols used with preferencefor preparing the prepolymers (Z.1.1) are therefore polyester diolswhich have been prepared using dimer fatty acids. Especially preferredare polyester diols in whose preparation at least 50 wt %, preferably 55to 75 wt %, of the dicarboxylic acids employed are dimer fatty acids.

Examples of corresponding polyols for preparing polyester polyols,preferably polyester diols, are ethylene glycol, 1,2- or1,3-propanediol, 1,2-, 1,3-, or 1,4-butanediol, 1,2-, 1,3-, 1,4-, or1,5-pentanediol, 1,2-, 1,3-, 1,4-, 1,5-, or 1,6-hexanediol, neopentylhydroxypivalate, neopentyl glycol, diethylene glycol, 1,2-, 1,3-, or1,4-cyclohexanediol, 1,2-, 1,3-, or 1,4-cyclohexanedimethanol, andtrimethylpentanediol. Diols are therefore used with preference. Suchpolyols and/or diols may of course also be used directly for preparingthe prepolymer (Z.1.1), in other words reacted directly withpolyisocyanates.

Further possibilities for use in preparing the prepolymers (Z.1.1) arepolyamines such as diamines and/or amino alcohols. Examples of diaminesinclude hydrazine, alkyl- or cycloalkyldiamines such as propylenediamine and 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, andexamples of amino alcohols include ethanolamine or diethanolamine.

The prepolymers (Z.1.1) comprise anionic groups and/or groups which canbe converted into anionic groups (that is, groups which can be convertedinto anionic groups by the use of known neutralizing agents, and alsoneutralizing agents specified later on below, such as bases). As theskilled person is aware, these groups are, for example, carboxylic,sulfonic and/or phosphonic acid groups, especially preferably carboxylicacid groups (functional groups which can be converted into anionicgroups by neutralizing agents), and also anionic groups derived from theaforementioned functional groups, such as, more particularly,carboxylate, sulfonate and/or phosphonate groups, preferably carboxylategroups. The introduction of such groups is known to increase thedispersibility in water. Depending on the conditions selected, thestated groups may be present proportionally or almost completely in theone form (carboxylic acid, for example) or the other form (carboxylate).One particular influencing factor resides, for example, in the use ofthe neutralizing agents which have already been addressed and which aredescribed in even more detail later on below. If the prepolymer (Z.1.1)is mixed with such neutralizing agents, then an amount of the carboxylicacid groups is converted into carboxylate groups, this amountcorresponding to the amount of the neutralizing agent. Irrespective ofthe form in which the stated groups are present, however, a uniformnomenclature is frequently selected in the context of the presentinvention, for greater ease of comprehension. Where, for example, aparticular acid number is specified for a polymer, such as for aprepolymer (Z.1.1), or where such a polymer is referred to ascarboxy-functional, this reference hereby always embraces not only thecarboxylic acid groups but also the carboxylate groups. If there is tobe any differentiation in this respect, such differentiation is dealtwith, for example, using the degree of neutralization.

In order to introduce the stated groups, it is possible, during thepreparation of the prepolymers (Z.1.1), to use starting compounds whichas well as groups for reaction in the preparation of urethane bonds,preferably hydroxyl groups, further comprise the abovementioned groups,carboxylic acid groups for example. In this way the groups in questionare introduced into the prepolymer.

Corresponding compounds contemplated for introducing the preferredcarboxylic acid groups are polyether polyols and/or polyester polyols,provided they contain carboxyl groups. However, compounds used withpreference are at any rate low molecular weight compounds which have atleast one carboxylic acid group and at least one functional groupreactive toward isocyanate groups, preferably hydroxyl groups. In thecontext of the present invention, the expression “low molecular weightcompound”, as opposed to higher molecular weight compounds, especiallypolymers, should be understood to mean those to which a discretemolecular weight can be assigned, as preferably monomeric compounds. Alow molecular weight compound is thus, more particularly, not a polymer,since the latter are always a mixture of molecules and have to bedescribed using mean molecular weights. Preferably, the term “lowmolecular weight compound” is understood to mean that the correspondingcompounds have a molecular weight of less than 300 g/mol. Preference isgiven to the range from 100 to 200 g/mol.

Compounds preferred in this context are, for example, monocarboxylicacids containing two hydroxyl groups, as for example dihydroxypropionicacid, dihydroxysuccinic acid, and dihydroxybenzoic acid. Very particularcompounds are alpha,alpha-dimethylolalkanoic acids such as2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid,2,2-dimethylolbutyric acid and 2,2-dimethylolpentanoic acid, especially2,2-dimethylolpropionic acid.

Preferably, therefore, the prepolymers (Z.1.1) are carboxy-functional.They preferably possess an acid number, based on the solids content, of10 to 35 mg KOH/g, more particularly 15 to 23 mg KOH/g (for measurementmethod, see Example section).

The number-average molecular weight of the prepolymers may vary widelyand is situated for example in the range from 2000 to 20 000 g/mol,preferably from 3500 to 6000 g/mol (for measurement method, see Examplesection).

The prepolymer (Z.1.1) contains isocyanate groups. Preferably, based onthe solids content, it possesses an isocyanate content of 0.5 to 6.0 wt%, preferably 1.0 to 5.0 wt %, especially preferably 1.5 to 4.0 wt %(for measurement method, see Example section).

Given that the prepolymer (Z.1.1) contains isocyanate groups, thehydroxyl number of the prepolymer is likely in general to be very low.The hydroxyl number of the prepolymer, based on the solids content, ispreferably less than 15 mg KOH/g, more particularly less than 10 mgKOH/g, even more preferably less than 5 mg KOH/g (for measurementmethod, see Example section).

The prepolymers (Z.1.1) may be prepared by known and established methodsin bulk or solution, especially preferably by reaction of the startingcompounds in organic solvents, such as preferably methyl ethyl ketone,at temperatures of, for example, 60 to 120° C., and optionally with useof catalysts typical for polyurethane preparation. Such catalysts areknown to those skilled in the art, one example being dibutyltin laurate.The procedure here is of course to select the proportion of the startingcomponents such that the product, in other words the prepolymer (Z.1.1),contains isocyanate groups. It is likewise directly apparent that thesolvents ought to be selected in such a way that they do not enter intoany unwanted reactions with the functional groups of the startingcompounds, in other words being inert toward these groups to the effectthat they do not hinder the reaction of these functional groups. Thepreparation is preferably actually carried out in an organic solvent(Z.2) as described later on below, since this solvent must in any casebe present in the composition (Z) for preparation in stage (I) of theprocess.

As already indicated above, the groups in the prepolymer (Z.1.1) whichcan be converted into anionic groups may also be present proportionallyas correspondingly anionic groups, as a result of the use of aneutralizing agent, for example. In this way it is possible to adjustthe water-dispersibility of the prepolymers (Z.1.1) and hence also ofthe intermediate (Z.1).

Neutralizing agents contemplated include, in particular, the known basicneutralizing agents such as, for example, carbonates,hydrogencarbonates, or hydroxides of alkali metals and alkaline earthmetals, such as LiOH, NaOH, KOH, or Ca(OH)₂ for example. Likewisesuitable for the neutralization and preferred for use in the context ofthe present invention are organic bases containing nitrogen, such asamines, such as ammonia, trimethylamine, triethylamine, tributylamines,dimethylaniline, triphenylamine, dimethylethanolamine,methyldiethanolamine, or triethanolamine, and also mixtures thereof.

The neutralization of the prepolymer (Z.1.1) with the neutralizingagents, more particularly with the nitrogen-containing organic bases,may take place after the preparation of the prepolymer in organic phase,in other words in solution with an organic solvent, more particularly asolvent (Z.2) as described later on below. The neutralizing agent may ofcourse also be added during or before the beginning of the actualpolymerization, in which case, for example, the starting compoundscontaining carboxylic acid groups are neutralized.

If neutralization of the groups which can be converted into anionicgroups, more particularly of the carboxylic acid groups, is desired, theneutralizing agent may be added, for example, in an amount such that aproportion of 35% to 65% of the groups is neutralized (degree ofneutralization). Preference is given to a range from 40% to 60% (formethod of calculation, see Example section).

The prepolymer (Z.1.1) is preferably neutralized as described after itspreparation and before its use for preparing the intermediate (Z.1).

The preparation described here of the intermediate (Z.1) involves thereaction of the above-described prepolymer (Z.1.1) with at least one,preferably precisely one, polyamine (Z.1.2a) derived from a polyamine(Z.1.2).

The polyamine (Z.1.2a) comprises two blocked primary amino groups andone or two free secondary amino groups.

Blocked amino groups, as is known, are those in which the hydrogenresidues on the nitrogen that are present inherently in free aminogroups have been substituted by reversible reaction with a blockingagent. In view of the blocking, the amino groups cannot be reacted likefree amino groups, via condensation reactions or addition reactions, andin this respect are therefore nonreactive, thereby differentiating themfrom free amino groups. The reactions known per se for the amino groupsare then evidently only enabled after the reversibly adducted blockingagent has been removed again, thereby producing in turn the free aminogroups. The principle therefore resembles the principle of capped orblocked isocyanates, which are likewise known within the field ofpolymer chemistry.

The primary amino groups of the polyamine (Z.1.2a) may be blocked withthe blocking agents that are known per se, as for example with ketonesand/or aldehydes. Such blocking in that case, with release of water,produces ketimines and/or aldimines which no longer contain anynitrogen-hydrogen bonds, meaning that typical condensation reactions oraddition reactions of an amino group with a further functional group,such as an isocyanate group, are unable to take place.

Reaction conditions for the preparation of a blocked primary amine ofthis kind, such as of a ketimine, for example, are known. Thus, forexample, such blocking may be realized with introduction of heat to amixture of a primary amine with an excess of a ketone which functions atthe same time as a solvent for the amine. The water of reaction formedis preferably removed during the reaction, in order to prevent thepossibility otherwise of reverse reaction (deblocking) of the reversibleblocking.

The reaction conditions for deblocking of blocked primary amino groupsare also known per se. For example, simply the transfer of a blockedamine to the aqueous phase is sufficient to shift the equilibrium backto the side of the deblocking, as a result of the concentration pressurethat then exists, exerted by the water, and thereby to generate freeprimary amino groups and also a free ketone, with consumption of water.

It follows from the above that in the context of the present invention,a clear distinction is being made between blocked and free amino groups.If, nevertheless, an amino group is specified neither as being blockednor as being free, the reference there is to a free amino group.

Preferred blocking agents for blocking the primary amino groups of thepolyamine (Z.1.2a) are ketones. Particularly preferred among the ketonesare those which constitute an organic solvent (Z.2) as described lateron below. The reason is that these solvents (Z.2) must be present in anycase in the composition (Z) for preparation in stage (I) of the process.It has already been indicated above that the preparation ofcorresponding primary amines blocked with a ketone proceeds toparticularly good effect in an excess of the ketone. Through the use ofketones (Z.2) for the blocking, therefore, it is possible to use thecorrespondingly preferred preparation procedure for blocked amines,without any need for costly and inconvenient removal of the blockingagent, which may be unwanted. Instead, the solution of the blocked aminecan be used directly in order to prepare the intermediate (Z.1).Preferred blocking agents are acetone, methyl ethyl ketone, methylisobutyl ketone, diisopropyl ketone, cyclopentanone, or cyclohexanone,particularly preferred agents are the ketones (Z.2) methyl ethyl ketoneand methyl isobutyl ketone.

The preferred blocking with ketones and/or aldehydes, more particularlyketones, and the accompanying preparation of ketimines and/or aldimines,has the advantage, moreover, that primary amino groups are blockedselectively. Secondary amino groups present are evidently unable to beblocked, and therefore remain free. Consequently a polyamine (Z.1.2a)which as well as the two blocked primary amino groups also contains oneor two free secondary amino groups can be prepared readily by way of thestated preferred blocking reactions from a polyamine (Z.1.2) whichcontains free secondary and primary amino groups.

The polyamines (Z.1.2a) may be prepared by blocking the primary aminogroups of polyamines (Z.1.2) containing two primary amino groups and oneor two secondary amino groups. Ultimately suitable are all aliphatic,aromatic, or araliphatic (mixed aliphatic-aromatic) polyamines (Z.1.2)which are known per se and which have two primary amino groups and oneor two secondary amino groups. This means that as well as the statedamino groups, there may per se be any aliphatic, aromatic, oraraliphatic groups present. Possible, for example, are monovalent groupslocated as terminal groups on a secondary amino group, or divalentgroups located between two amino groups.

Aliphatic in the context of the present invention is an epithetreferring to all organic groups which are not aromatic. For example, thegroups present as well as the stated amino groups may be aliphatichydrocarbon groups, in other words groups which consist exclusively ofcarbon and hydrogen and which are not aromatic. These aliphatichydrocarbon groups may be linear, branched, or cyclic, and may besaturated or unsaturated. These groups may of course also include bothcyclic and linear or branched moieties. It is also possible foraliphatic groups to contain heteroatoms, more particularly in the formof bridging groups such as ether, ester, amide and/or urethane groups.Possible aromatic groups are likewise known and require no furtherelucidation.

The polyamines (Z.1.2a) preferably possess two blocked primary aminogroups and one or two free secondary amino groups, and as primary aminogroups they possess exclusively blocked primary amino groups, and assecondary amino groups they possess exclusively free secondary aminogroups.

Preferably, in total, the polyamines (Z.1.2a) possess three or fouramino groups, these groups being selected from the group consisting ofthe blocked primary amino groups and of the free secondary amino groups.

Especially preferred polyamines (Z.1.2a) are those which consist of twoblocked primary amino groups, one or two free secondary amino groups,and also aliphatically saturated hydrocarbon groups.

Analogous preferred embodiments apply to the polyamines (Z.1.2), freeprimary amino groups then being present therein instead of blockedprimary amino groups.

Examples of preferred polyamines (Z.1.2) from which polyamines (Z.1.2a)may also be prepared by blocking of the primary amino groups arediethylenetriamine, 3-(2-aminoethyl)aminopropylamine,dipropylene-triamine, and alsoN1-(2-(4-(2-aminoethyl)piperazin-1-yl)ethyl)ethane-1,2-diamine (onesecondary amino group, two primary amino groups for blocking) andtriethylenetetramine, and also N,N′-bis(3-aminopropyl)ethylenediamine(two secondary amino groups, two primary amino groups for blocking).

To the skilled person it is clear that not least for reasons associatedwith pure technical synthesis, there cannot always be a theoreticallyidealized quantitative conversion in the blocking of primary aminogroups. For example, if a particular amount of a polyamine is blocked,the proportion of the primary amino groups that are blocked in theblocking process may be, for example, 95 mol % or more (determinable byIR spectroscopy; see Example section). Where a polyamine in thenonblocked state, for example, possesses two free primary amino groups,and where the primary amino groups of a certain quantity of this amineare then blocked, it is said in the context of the present inventionthat this amine has two blocked primary amino groups if a fraction ofmore than 95 mol % of the primary amino groups present in the quantityemployed are blocked. This is due on the one hand to the fact, alreadystated, that from a technical synthesis standpoint, a quantitativeconversion cannot always be realized. On the other hand, the fact thatmore than 95 mol % of the primary amino groups are blocked means thatthe major fraction of the total amount of the amines used for blockingdoes in fact contain exclusively blocked primary amino groups,specifically exactly two blocked primary amino groups.

The preparation of the intermediate (Z.1) involves the reaction of theprepolymer (Z.1.1) with the polyamine (Z.1.2a) by addition reaction ofisocyanate groups from (Z.1.1) with free secondary amino groups from(Z.1.2a). This reaction, which is known per se, then leads to theattachment of the polyamine (Z.1.2a) onto the prepolymer (Z.1.1), withformation of urea bonds, ultimately forming the intermediate (Z.1). Itwill be readily apparent that in the preparation of the intermediate(Z.1), preference is thus given to not using any other amines havingfree or blocked secondary or free or blocked primary amino groups.

The intermediate (Z.1) can be prepared by known and establishedtechniques in bulk or solution, especially preferably by reaction of(Z.1.1) with (Z.1.2a) in organic solvents. It is immediately apparentthat the solvents ought to be selected in such a way that they do notenter into any unwanted reactions with the functional groups of thestarting compounds, and are therefore inert or largely inert in theirbehavior toward these groups. As solvent in the preparation, preferenceis given to using, at least proportionally, an organic solvent (Z.2) asdescribed later on below, especially methyl ethyl ketone, even at thisstage, since this solvent must in any case be present in the composition(Z) to be prepared in stage (I) of the process. With preference asolution of a prepolymer (Z.1.1) in a solvent (Z.2) is mixed with asolution of a polyamine (Z.1.2a) in a solvent (Z.2), and the reactiondescribed can take place.

Of course, the intermediate (Z.1) thus prepared may be neutralizedduring or after the preparation, using neutralizing agents alreadydescribed above, in the manner likewise described above for theprepolymer (Z.1.1). It is nevertheless preferred for the prepolymer(Z.1.1) to be neutralized prior to its use for preparing theintermediate (Z.1), in a manner described above, so that neutralizationduring or after the preparation of (Z.1) is no longer relevant. In sucha case, therefore, the degree of neutralization of the prepolymer(Z.1.1) can be equated with the degree of neutralization of theintermediate (Z.1). Where there is no further addition of neutralizingagents at all in the context of the process, therefore, the degree ofneutralization of the polymers present in the ultimately prepareddispersions (PD) of the invention can also be equated with the degree ofneutralization of the prepolymer (Z.1.1).

The intermediate (Z.1) possesses blocked primary amino groups. This canevidently be achieved in that the free secondary amino groups arebrought to reaction in the reaction of the prepolymer (Z.1.1) and of thepolyamine (Z.1.2a), but the blocked primary amino groups are notreacted. Indeed, as already described above, the effect of the blockingis that typical condensation reactions or addition reactions with otherfunctional groups, such as isocyanate groups, are unable to take place.This of course means that the conditions for the reaction should beselected such that the blocked amino groups also remain blocked, inorder thereby to provide an intermediate (Z.1). The skilled person knowshow to set such conditions, which are brought about, for example, byreaction in organic solvents, which is preferred in any case.

The intermediate (Z.1) contains isocyanate groups. Accordingly, in thereaction of (Z.1.1) and (Z.1.2a), the ratio of these components must ofcourse be selected such that the product—that is, the intermediate(Z.1)—contains isocyanate groups.

Since, as described above, in the reaction of (Z.1.1) with (Z.1.2a),free secondary amino groups are reacted with isocyanate groups, but theprimary amino groups are not reacted, owing to the blocking, it is firstof all immediately clear that in this reaction the molar ratio ofisocyanate groups from (Z.1.1) to free secondary amino groups from(Z.1.2a) must be greater than 1. This feature arises implicitly,nevertheless clearly and directly from the feature essential to theinvention, namely that the intermediate (Z.1) contains isocyanategroups.

It is nevertheless preferred for there to be an excess of isocyanategroups, defined as below, during the reaction. The molar amounts (n) ofisocyanate groups, free secondary amino groups, and blocked primaryamino groups, in this preferred embodiment, satisfy the followingcondition: [n (isocyanate groups from (Z.1.1))−n (free secondary aminogroups from (Z.1.2a))]/n (blocked primary amino groups from(Z.1.2a))=1.2/1 to 4/1, preferably 1.5/1 to 3/1, very preferably 1.8/1to 2.2/1, even more preferably 2/1.

In this preferred embodiment, the intermediate (Z.1), formed by reactionof isocyanate groups from (Z.1.1) with the free secondary amino groupsfrom (Z.1.2a), possesses an excess of isocyanate groups in relation tothe blocked primary amino groups. This excess is ultimately achieved byselecting the molar ratio of isocyanate groups from (Z.1.1) to the totalamount of free secondary amino groups and blocked primary amino groupsfrom (Z.1.2a) to be large enough that even after the preparation of(Z.1) and the corresponding consumption of isocyanate groups by thereaction with the free secondary amino groups, there remains acorresponding excess of the isocyanate groups.

Where, for example, the polyamine (Z.1.2a) has one free secondary aminogroup and two blocked primary amino groups, the molar ratio between theisocyanate groups from (Z.1.1) to the polyamine (Z.1.2a) in theespecially preferred embodiment is set at 5/1. The consumption of oneisocyanate group in the reaction with the free secondary amino groupwould then mean that 4/2 (or 2/1) was realized for the condition statedabove.

The fraction of the intermediate (Z.1) is from 15 to 65 wt %, preferablyfrom 25 to 60 wt %, more preferably from 30 to 55 wt %, especiallypreferably from 35 to 52.5 wt %, and, in one very particular embodiment,from 40 to 50 wt %, based in each case on the total amount of thecomposition (Z).

Determining the fraction of an intermediate (Z.1) may be carried out asfollows: The solids content of a mixture which besides the intermediate(Z.1) contains only organic solvents is ascertained (for measurementmethod for determining the solids (also called solids content, seeExample section). The solids content then corresponds to the amount ofthe intermediate (Z.1). By taking account of the solids content of themixture, therefore, it is possible to determine or specify the fractionof the intermediate (Z.1) in the composition (Z). Given that theintermediate (Z.1) is preferably prepared in an organic solvent anyway,and therefore, after the preparation, is in any case present in amixture which comprises only organic solvents apart from theintermediate, this is the technique of choice.

The composition (Z) further comprises at least one specific organicsolvent (Z.2).

The solvents (Z.2) possess a solubility in water of not more than 38 wt% at a temperature of 20° C. (for measurement method, see Examplesection). The solubility in water at a temperature of 20° C. ispreferably less than 30 wt %. A preferred range is from 1 to 30 wt %.

The solvent (Z.2) accordingly possesses a fairly moderate solubility inwater, being in particular not fully miscible with water or possessingno infinite solubility in water. A solvent is fully miscible with waterwhen it can be mixed in any proportions with water without occurrence ofseparation, in other words of the formation of two phases.

Examples of solvents (Z.2) are methyl ethyl ketone, methyl isobutylketone, diisobutyl ketone, diethyl ether, dibutyl ether, dipropyleneglycol dimethyl ether, ethylene glycol diethyl ether, toluene, methylacetate, ethyl acetate, butyl acetate, propylene carbonate,cyclohexanone, or mixtures of these solvents. Preference is given tomethyl ethyl ketone, which has a solubility in water of 24 wt % at 20°C.

No specific organic solvents (Z.2) are therefore solvents such asacetone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, tetrahydrofuran,dioxane, N-formylmorpholine, dimethylformamide, or dimethyl sulfoxide.

A particular effect of selecting the specific solvents (Z.2) of onlylimited solubility in water is that when the composition (Z) isdispersed in aqueous phase, in step (II) of the process, a homogeneoussolution cannot be directly formed. It is assumed that the dispersionthat is present instead makes it possible for the crosslinking reactionsthat occur as part of step (II) (addition reactions of free primaryamino groups and isocyanate groups to form urea bonds) to take place ina restricted volume, thereby ultimately allowing the formation of themicroparticles defined as above.

As well as having the water-solubility described, preferred solvents(Z.2) possess a boiling point of not more than 120° C., more preferablyof not more than 90° C. (under atmospheric pressure, in other words1.013 bar). This has advantages in the context of step (III) of theprocess, said step being described later on below, in other words the atleast partial removal of the at least one organic solvent (Z.2) from thedispersion prepared in step (II) of the process. The reason is evidentlythat, when using the solvents (Z.2) that are preferred in this context,these solvents can be removed by distillation, for example, without theremoval simultaneously of significant quantities of the water introducedin step (II) of the process. There is therefore no need, for example,for the laborious re-addition of water in order to retain the aqueousnature of the dispersion (PD).

The fraction of the at least one organic solvent (Z.2) is from 35 to 85wt %, preferably from 40 to 75 wt %, more preferably from 45 to 70 wt %,especially preferably from 47.5 to 65 wt %, and, in one very particularembodiment, from 50 to 60 wt %, based in each case on the total amountof the composition (Z).

In the context of the present invention it has emerged that through thespecific combination of a fraction as specified above for theintermediate (Z.1) in the composition (Z), and through the selection ofthe specific solvents (Z.2) it is possible, after the below-describedsteps (II) and (III), to provide polyurethane-polyurea dispersions whichcomprise polyurethane-polyurea particles having the requisite particlesize, which further have the requisite gel fraction.

The components (Z.1) and (Z.2) described preferably make up in total atleast 90 wt % of the composition (Z). Preferably the two components makeup at least 95 wt %, more particularly at least 97.5 wt %, of thecomposition (Z). With very particular preference, the composition (Z)consists of these two components. In this context it should be notedthat where neutralizing agents as described above are used, theseneutralizing agents are ascribed to the intermediate when calculatingthe amount of an intermediate (Z.1). The reason is that in this case theintermediate (Z.1) at any rate possesses anionic groups, which originatefrom the use of the neutralizing agent. Accordingly, the cation that ispresent after these anionic groups have formed is likewise ascribed tothe intermediate.

Where the composition (Z) includes other components, in addition tocomponents (Z.1) and (Z.2), these other components are preferably justorganic solvents. The solids content of the composition (Z) thereforecorresponds preferably to the fraction of the intermediate (Z.1) in thecomposition (Z). The composition (Z) therefore possesses preferably asolids content of 15 to 65 wt %, preferably of 25 to 60 wt %, morepreferably of 30 to 55 wt %, especially preferably of 35 to 52.5 wt %,and, in one especially preferred embodiment, of 40 to 50 wt %.

A particularly preferred composition (Z) therefore contains in total atleast 90 wt % of components (Z.1) and (Z.2), and other than theintermediate (Z.1) includes exclusively organic solvents.

An advantage of the composition (Z) is that it can be prepared withoutthe use of eco-unfriendly and health-injurious organic solvents such asN-methyl-2-pyrrolidone, dimethylformamide, dioxane, tetrahydrofuran, andN-ethyl-2-pyrrolidone. Preferably, accordingly, the composition (Z)contains less than 10 wt %, preferably less than 5 wt %, more preferablyless than 2.5 wt % of organic solvents selected from the groupconsisting of N-methyl-2-pyrrolidone, dimethylformamide, dioxane,tetrahydrofuran, and N-ethyl-2-pyrrolidone. The composition (Z) ispreferably entirely free from these organic solvents.

In a second step (II) of the process described here, the composition (Z)is dispersed in aqueous phase.

It is known, and also follows from what has already been said above,that in step (II), therefore, there is a deblocking of the blockedprimary amino groups of the intermediate (Z.1). Indeed, as a result ofthe transfer of a blocked amine to the aqueous phase, the reversiblyattached blocking agent is released, with consumption of water, and freeprimary amino groups are formed.

It is likewise clear, therefore, that the resulting free primary aminogroups are then reacted with isocyanate groups likewise present in theintermediate (Z.1), or in the deblocked intermediate formed from theintermediate (Z.1), by addition reaction, with formation of urea bonds.

It is also known that the transfer to the aqueous phase means that it ispossible in principle for the isocyanate groups in the intermediate(Z.1), or in the deblocked intermediate formed from the intermediate(Z.1), to react with the water, with elimination of carbon dioxide, toform free primary amino groups, which can then be reacted in turn withisocyanate groups still present.

Of course, the reactions and conversions referred to above proceed inparallel with one another. Ultimately, as a result, for example, ofintermolecular and intramolecular reaction or crosslinking, a dispersionis formed which comprises polyurethane-polyurea particles with definedaverage particle size and with defined degree of crosslinking or gelfraction.

In step (II) of the process described here, the composition (Z) isdispersed in water, there being a deblocking of the blocked primaryamino groups of the intermediate (Z.1) and a reaction of the resultingfree primary amino groups with the isocyanate groups of the intermediate(Z.1) and also with the isocyanate groups of the deblocked intermediateformed from the intermediate (Z.1), by addition reaction.

Step (II) of the process described here, in other words the dispersingin aqueous phase, may take place in any desired way. This means thatultimately the only important thing is that the composition (Z) is mixedwith water or with an aqueous phase. With preference, the composition(Z), which after the preparation may be for example at room temperature(in other words 20° C.) or at a temperature increased relative to roomtemperature, of 30 to 60° C., for example, can be stirred into water,producing a dispersion. The water already introduced has roomtemperature, for example. Dispersion may take place in pure water(deionized water), meaning that the aqueous phase consists solely ofwater, this being preferred. Besides water, of course, the aqueous phasemay also include, proportionally, typical auxiliaries such as typicalemulsifiers and protective colloids. A compilation of suitableemulsifiers and protective colloids is found in, for example, HoubenWeyl, Methoden der organischen Chemie [Methods of Organic Chemistry],volume XIV/1 Makromolekulare Stoffe [Macromolecular compounds], GeorgThieme Verlag, Stuttgart 1961, p. 411 ﬀ.

It is of advantage if in stage (II) of the process, in other words atthe dispersing of the composition (Z) in aqueous phase, the weight ratioof organic solvents and water is selected such that the resultingdispersion has a weight ratio of water to organic solvents of greaterthan 1, preferably of 1.05 to 2/1, especially preferably of 1.1 to1.5/1.

In step (III) of the process described here, the at least one organicsolvent (Z.2) is removed at least partly from the dispersion obtained instep (II). Of course, step (III) of the process may also entail removalof other solvents as well, possibly present, for example, in thecomposition (Z).

The removal of the at least one organic solvent (Z.2) and of any furtherorganic solvents may be accomplished in any way which is known, as forexample by vacuum distillation at temperatures slightly raised relativeto room temperature, of 30 to 60° C., for example.

The resulting polyurethane-polyurea dispersion (PD) is aqueous(regarding the basic definition of “aqueous”, see earlier on above).

A particular advantage of the dispersion (PD) for use in accordance withthe invention is that it can be formulated with only very smallfractions of organic solvents, yet enables the advantages described atthe outset in accordance with the invention. The dispersion (PD) for usein accordance with the invention contains preferably not more than 15.0wt %, especially preferably not more than 10 wt %, very preferably notmore than 5 wt % and once again preferably not more than 2.5 wt % oforganic solvents (for measurement method, see Example section).

The fraction of the polyurethane-polyurea polymer in the dispersion (PD)is preferably 25 to 55 wt %, preferably 30 to 50 wt %, more preferably35 to 45 wt %, based in each case on the total amount of the dispersion(determined as for the determination described above for theintermediate (Z.1) via the solids content).

The fraction of water in the dispersion (PD) is preferably 45 to 75 wt%, preferably 50 to 70 wt %, more preferably 55 to 65 wt %, based ineach case on the total amount of the dispersion.

It is a particular advantage of the dispersion (PD) for inventive usethat it can be formulated in such a way that it consists to an extent ofat least 90 wt %, preferably at least 92.5 wt %, very preferably atleast 95 wt %, and more preferably at least 97.5 wt %, of thepolyurethane-polyurea particles and water (the associated value isobtained by summing the amount of the particles (that is, of thepolymer, determined via the solids content) and the amount of water). Ithas emerged that in spite of this small fraction of further componentssuch as organic solvents in particular, the dispersions are in any casevery stable, especially storage-stable. In this way, two relevantadvantages are combined. First, dispersions are provided which can beused in aqueous basecoat materials, where they lead to the applicationsadvantages described at the outset and also in the examples to follow.Secondly, however, a commensurate freedom of formulation in theproduction of aqueous basecoat materials is achieved. This means thatadditional fractions of organic solvents can be used in the basecoatmaterials, as are necessary, for example, in order to formulatedifferent components commensurately. At the same time, however, there isno threat to the fundamentally aqueous nature of the basecoat material.On the contrary: the basecoat materials can still be formulated withcomparatively low fractions of organic solvents, and they therefore havea particularly good environmental profile.

Even more preferred is for the dispersion, other than the polymer, toinclude only water and any organic solvents, in the form, for example,of residual fractions, not fully removed in stage (III) of the process.The solids content of the dispersion (PD) is therefore preferably 25% to55%, preferably 30% to 50%, more preferably 35% to 45%, and morepreferably still is in agreement with the fraction of the polymer in thedispersion.

An advantage of the dispersion (PD) is that it can be prepared withoutthe use of eco-unfriendly and health-injurious organic solvents such asN-methyl-2-pyrrolidone, dimethylformamide, dioxane, tetrahydrofuran, andN-ethyl-2-pyrrolidone. Accordingly the dispersion (PD) containspreferably less than 7.5 wt %, preferably less than 5 wt %, morepreferably less than 2.5 wt % of organic solvents selected from thegroup consisting of N-methyl-2-pyrrolidone, dimethylformamide, dioxane,tetrahydrofuran, and N-ethyl-2-pyrrolidone. The dispersion (PD) ispreferably entirely free from these organic solvents.

Based on the solids content, the polyurethane-polyurea polymer presentin the dispersion preferably possesses an acid number of 10 to 35 mgKOH/g, more particularly of 15 to 23 mg KOH/g (for measurement method,see Example section).

The polyurethane-polyurea polymer present in the dispersion preferablypossesses hardly any hydroxyl groups, or none. The OH number of thepolymer, based on the solids content, is preferably less than 15 mgKOH/g, more particularly less than 10 mg KOH/g, more preferably stillless than 5 mg KOH/g (for measurement method, see Example section).

The fraction of the dispersions (PD) for use in accordance with theinvention, based on the total weight of the pigmented aqueous basecoatmaterial, is preferably 2.5 to 60 wt %, more preferably 10 to 50 wt %,and very preferably 15 to 40 wt % or even 15 to 30 wt %.

The fraction of the polyurethane-polyurea polymers originating from thedispersions (PD), based on the total weight of the aqueous basecoatmaterial, is preferably from 0.6 to 33.0 wt %, preferably 3.0 to 25.0 wt%, more preferably 5.0 to 18.0 wt %.

Determining or specifying the fraction of the polyurethane-polyureapolymers originating from the dispersions (PD) in the basecoat materialmay be done via the determination of the solids content of a dispersion(PD) for use in accordance with the invention which is to be used in thebasecoat material.

In the case of a possible particularization to basecoat materialscomprising preferred dispersions (PD) in a specific proportional range,the following applies. The dispersions (PD) which do not fall within thepreferred group may of course still be present in the basecoat material.In that case the specific proportional range applies only to thepreferred group of dispersions (PD). It is preferred nonetheless for thetotal proportion of dispersions (PD), consisting of dispersions from thepreferred group and dispersions which are not part of the preferredgroup, to be subject likewise to the specific proportional range.

In the case of restriction to a proportional range of 3 to 25 wt % andto a preferred group of dispersions (PD), therefore, this proportionalrange evidently applies initially only to the preferred group ofdispersions (PD). In that case, however, it would be preferable forthere to be likewise from 3 to 25 wt % in total present of alloriginally encompassed dispersions, consisting of dispersions from thepreferred group and dispersions which do not form part of the preferredgroup. If, therefore, 15 wt % of dispersions (PD) of the preferred groupare used, not more than 10 wt % of the dispersions of the non-preferredgroup may be used.

The stated principle is valid, for the purposes of the presentinvention, for all stated components of the basecoat material and fortheir proportional ranges—for example, for the pigments specified lateron below, or else for the crosslinking agents specified later on below,such as melamine resins.

The basecoat material for use in accordance with the inventionpreferably comprises at least one pigment.

These are understood to mean coloring and/or visual effect pigmentsknown per se.

Such color pigments and effect pigments are known to those skilled inthe art and are described, for example, in Römpp-Lexikon Lacke andDruckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, pages 176and 451. The terms “coloring pigment” and “color pigment” areinterchangeable, just like the terms “visual effect pigment” and “effectpigment”.

Preferred effect pigments are, for example, platelet-shaped metal effectpigments such as lamellar aluminum pigments, gold bronzes, oxidizedbronzes and/or iron oxide-aluminum pigments, pearlescent pigments suchas pearl essence, basic lead carbonate, bismuth oxide chloride and/ormetal oxide-mica pigments and/or other effect pigments such as lamellargraphite, lamellar iron oxide, multilayer effect pigments composed ofPVD films and/or liquid crystal polymer pigments. Particularly preferredare platelet-shaped metal effect pigments, more particularly lamellaraluminum pigments.

Typical color pigments especially include inorganic coloring pigmentssuch as white pigments such as titanium dioxide, zinc white, zincsulfide or lithopone; black pigments such as carbon black, ironmanganese black, or spinel black; chromatic pigments such as chromiumoxide, chromium oxide hydrate green, cobalt green or ultramarine green,cobalt blue, ultramarine blue or manganese blue, ultramarine violet orcobalt violet and manganese violet, red iron oxide, cadmiumsulfoselenide, molybdate red or ultramarine red; brown iron oxide, mixedbrown, spinel phases and corundum phases or chromium orange; or yellowiron oxide, nickel titanium yellow, chromium titanium yellow, cadmiumsulfide, cadmium zinc sulfide, chromium yellow or bismuth vanadate.

The fraction of the pigments is preferably situated in the range from1.0 to 30.0 wt %, preferably 1.5 to 20.0 wt %, more preferably 2.0 to15.0 wt %, based in each case on the total weight of the aqueousbasecoat material.

Through the use of the dispersion (PD) and of the polymer presenttherein, the basecoat material of the invention comprises curablebinders. A “binder” in the context of the present invention and inaccordance with relevant DIN EN ISO 4618 is the nonvolatile component ofa coating composition, without pigments and fillers. Specific binders,accordingly, also include, for example, typical coatings additives, thepolymer present in the dispersion (PD), or further polymers which can beused, as described below, and typical crosslinking agents as describedbelow. Hereinafter, however, the expression, for the sake simply ofbetter clarity, is used principally in relation to particular physicallycurable polymers which optionally may also be thermally curable,examples being the polymers in the dispersions (PD), or else differentpolyurethanes, polyesters, polyacrylates and/or copolymers of the statedpolymers.

In the context of the present invention, the term “physical curing”means the formation of a film through loss of solvents from polymersolutions or polymer dispersions. Typically, no crosslinking agents arenecessary for this curing.

In the context of the present invention, the term “thermal curing”denotes the heat-initiated crosslinking of a coating film, with eitherself-crosslinking binders or else a separate crosslinking agent, incombination with a polymer as binder, (external crosslinking), beingused in the parent coating material. The crosslinking agent comprisesreactive functional groups which are complementary to the reactivefunctional groups present in the binders. As a result of the reaction ofthe groups, there is then crosslinking and hence, ultimately, theformation of a macroscopically crosslinked coating film.

It is clear that the binder components present in a coating materialalways exhibit at least a proportion of physical curing. If, therefore,it is said that a coating material comprises binder components which arethermally curable, this of course does not rule out the curing includinga proportion of physical curing as well.

The basecoat material of the invention preferably further comprises atleast one polymer as binder that is different from thepolyurethane-polyurea polymer present in the dispersion (PD), moreparticularly at least one polymer selected from the group consisting ofpolyurethanes, polyesters, polyacrylates and/or copolymers of the statedpolymers, more particularly polyesters and/or polyurethanepolyacrylates. Preferred polyesters are described, for example, in DE4009858 A1 in column 6 line 53 to column 7 line 61 and column 10 line 24to column 13 line 3 or in US 2014/0065428 A1 page 2 [0025] to [0035].Preferred polyurethane-polyacrylate copolymers (acrylated polyurethanes)and their preparation are described in, for example, WO 91/15528 A1,page 3, line 21 to page 20, line 33, and DE 4437535 A1, page 2, line 27to page 6, line 22. The described polymers as binders are preferablyhydroxy-functional and especially preferably possess an OH number in therange from 20 to 200 mg KOH/g, more preferably from 50 to 150 mg KOH/g.The basecoat materials of the invention more preferably comprise atleast one hydroxy-functional polyurethane-polyacrylate copolymer, morepreferably still at least one hydroxy-functionalpolyurethane-polyacrylate copolymer and also at least onehydroxy-functional polyester.

The proportion of the further polymers as binders may vary widely and issituated preferably in the range from 0.5 to 20.0 wt %, more preferably1.0 to 15.0 wt %, very preferably 1.5 to 10.0 wt %, based in each caseon the total weight of the basecoat material of the invention.

The basecoat material of the invention preferably further comprises atleast one typical crosslinking agent known per se. It preferablycomprises, as a crosslinking agent, at least one aminoplast resin and/ora blocked polyisocyanate, preferably an aminoplast resin. Among theaminoplast resins, melamine resins in particular are preferred.

The proportion of the crosslinking agents, more particularly aminoplastresins and/or blocked polyisocyanates, very preferably aminoplast resinsand, of these, preferably melamine resins, is preferably in the rangefrom 0.5 to 20.0 wt %, more preferably 1.0 to 15.0 wt %, very preferably1.5 to 10.0 wt %, based in each case on the total weight of the basecoatmaterial of the invention.

Preferably, the coating composition of the invention additionallycomprises at least one thickener.

Suitable thickeners are inorganic thickeners from the group of thephyllosilicates such as lithium aluminum magnesium silicates. It isnevertheless known that coating materials whose profile of rheologicalproperties is determined via the primary or predominant use of suchinorganic thickeners are in need of improvement in terms of their solidscontent, in other words can be formulated only with decidedly low solidscontents of less than 20%, for example, without detriment to importantapplications properties. A particular advantage of the basecoat materialof the invention is that it can be formulated without, or without agreat fraction of, such inorganic phyllosilicates employed asthickeners. Accordingly, the fraction of inorganic phyllosilicates usedas thickeners, based on the total weight of the basecoat material, ispreferably less than 0.5 wt %, especially preferably less than 0.1 wt %,and more preferably still less than 0.05 wt %. With very particularpreference, the basecoat material is entirely free of such inorganicphyllosilicates used as thickeners.

Instead, the basecoat material preferably comprises at least one organicthickener, as for example a (meth)acrylic acid-(meth)acrylate copolymerthickener or a polyurethane thickener. Employed with preference areassociative thickeners, such as the associative polyurethane thickenersknown per se, for example. Associative thickeners, as is known, arewater-soluble polymers which have strongly hydrophobic groups at thechain ends or in side chains, and/or whose hydrophilic chains containhydrophobic blocks or concentrations in their interior. As a result,these polymers possess a surfactant character and are capable of formingmicelles in aqueous phase. In similarity with the surfactants, thehydrophilic regions remain in the aqueous phase, while the hydrophobicregions enter into the particles of polymer dispersions, adsorb on thesurface of other solid particles such as pigments and/or fillers, and/orform micelles in the aqueous phase. Ultimately a thickening effect isachieved, without any increase in sedimentation behavior. Thickeners ofthis kind are available commercially, as for example under the tradename Adekanol (from Adeka Corporation).

The proportion of the organic thickeners is preferably in the range from0.01 to 5.0 wt %, more preferably 0.02 to 3.0 wt %, very preferably 0.05to 3.0 wt %, based in each case on the total weight of the basecoatmaterial of the invention.

Furthermore, the basecoat material of the invention may further compriseat least one further adjuvant. Examples of such adjuvants are saltswhich are thermally decomposable without residue or substantiallywithout residue, polymers as binders that are curable physically,thermally and/or with actinic radiation and that are different from thepolymers already stated as binders, further crosslinking agents,reactive diluents, transparent pigments, fillers, molecularlydispersively soluble dyes, nanoparticles, light stabilizers,antioxidants, deaerating agents, emulsifiers, slip additives,polymerization inhibitors, initiators of radical polymerizations,adhesion promoters, flow control agents, film-forming assistants, sagcontrol agents (SCAs), flame retardants, corrosion inhibitors, waxes,siccatives, biocides, and matting agents. Such adjuvants are used in thecustomary and known amounts.

The solids content of the basecoat material of the invention may varyaccording to the requirements of the case in hand. The solids content isguided primarily by the viscosity that is needed for application, moreparticularly spray application. A particular advantage is that thebasecoat material of the invention, for a comparatively high solidscontent, is able nevertheless to have a viscosity which allowsappropriate application and has a stable long-term viscosity whichimparts good storage stability.

The solids content of the basecoat material of the invention ispreferably at least 25%, more preferably at least 27.5%, especiallypreferably from 27.5% to 55%.

Under the stated conditions, in other words at the stated solidscontents, preferred basecoat materials of the invention have a viscosityof 40 to 180 mPa·s, more particularly 50 to 150 mPa·s and even morepreferably from 60 to 135 mPa·s over a period of 20 days, at 23° C.under a shearing load of 1000 l/s (for further details regarding themeasurement method, see Example section). For the purposes of thepresent invention, a viscosity within this range under the statedshearing load is referred to as long-term viscosity (storage viscosity).It is a measure of the storage stability of the basecoat material of theinvention and directly influences the stabilization of the microgeldispersion via the specific solvent composition.

The basecoat material of the invention is aqueous (regarding thedefinition of “aqueous”, see above).

The fraction of water in the basecoat material of the invention ispreferably at least 35 wt %, preferably at least 40 wt %, and morepreferably from 45 to 60 wt %.

Even more preferred is for the percentage sum of the solids content ofthe basecoat material and the fraction of water in the basecoat materialto be at least 70 wt %, preferably at least 80 wt %. Among thesefigures, preference is given to ranges of 70 to wt %, in particular 80to 90 wt %. In this reporting, the solids content, which traditionallyonly possesses the unit “%”, is reported in “wt %”. Since the solidscontent ultimately also represents a percentage weight figure, this formof representation is justified. If, then, a basecoat material has asolids content of 35% and a water content of 50 wt %, for example, thepercentage sum defined above, from the solids content of the basecoatmaterial and the fraction of water in the basecoat material, is 85 wt %.

This means that preferred basecoat materials of the invention containcomponents that are in principle a burden on the environment, such asorganic solvents in particular, at a comparatively low fraction of, forexample, less than 30 wt %, preferably less than 20 wt %. Preferredranges are from 10 to 30 wt %, more particularly 10 to 20 wt %.

The aqueous basecoat material for inventive use has a characteristicfeature wherein, based on the total amount of solvents (L) present inthe basecoat material, it contains in total less than 9 wt % of solventsselected from the group consisting of organic solvents (L1) having a HLBof between 5 and 15 and a water solubility of >1.5 wt % at 20° C.

The HLB of a solvent (L) here describes the ratio of the molar mass ofthe hydrophilic to the lipophilic fraction (hydrophilic-lipophilicbalance according to W. C. Griffin) of the solvent, and in this contextis defined as follows:

HLB(L)=20*(1−M(lipophilic fraction of (L))/M(L)),

the lipophilic fraction of the solvent (L) being made up of thefollowing carbon-containing groups:

every group CH_(n) with n=1 to 3, provided that the group

(i) is not in alpha position to OH, NH₂, CO₂H,

(ii) is not in ethylene oxide units located in an ethylene oxide chainhaving a terminal OH group, and/or

(iii) is not in a cyclic molecule or molecular moiety in alpha positionto a bridging functional group selected from —O—, NH—.

All other groups, examples being other carbon-containing groups ornon-carbon-containing groups, belong, accordingly to the hydrophilicfraction.

A solvent, accordingly, is constructed from a hydrophilic and/orlipophilic fraction. If a solvent is only constructed from a lipophilicfraction, it has a HLB of 0 (“zero”). Consequently a HLB of 20accompanies an exclusive hydrophilic fraction. Solvents with hydrophilicand lipophilic fractions have HLB values of between 0 and 20. The molarmass of lipophilic groups here is determined according to the criteriaspecified above, and is divided by the total molar mass of the solvent.This fraction, as indicated in the HLB formula, is subtracted from afigure of one. The result is multiplied by 20. Examples that may bementioned at this point are the solvents cyclohexane, with a HLB of 0,isopropanol, with a HLB of 10.0, and diethylene glycol, with a HLB of20.

The solvents (L1), to be used in the sense of the invention at less than9 wt %, more preferably at less than 7.5 wt %, especially preferably atless than 6.0 wt %, and even more especially preferably at less than 5wt %, based on the total amount of solvents (L) present in the basecoatmaterial, are distinguished by a HLB of between 5 and 15 and a watersolubility of >1.5 wt % at 20° C. (for solubility measurement method,see Example section).

As examples, but not conclusively, the following solvents (L1) of thiscategory, confined to less than 9 wt %, may be stated together withtheir respective HLB and also their water solubility in wt % at 20° C.:ethanol (HLB 13.5; water solubility infinite), butyl diglycol (HLB 13.0;water solubility infinite), tetrahydrofuran (HLB 12.2; water solubilityinfinite), butyl glycol (HLB 10.3; water solubility infinite),n-propanol (HLB 10.3; water solubility infinite), isopropanol (HLB 10.0;water solubility infinite), acetone (HLB 9.7; water solubilityinfinite), 1-methoxy-2-propyl acetate (HLB 9.1; water solubility 22.0),dipropylene glycol monomethyl ether (HLB 8.4; water solubilityinfinite), n-butanol (HLB 8.4; water solubility 7.7), isobutanol (HLB8.4; water solubility 9.5), 1-propoxy-2-propanol (HLB 7.8; watersolubility infinite), butanone (HLB 7.8; water solubility 35.3),cyclohexanone (HLB 5.7; water solubility 2.3), methyl isobutyl ketone(HLB 5.6; water solubility 1.9).

Only with compliance with the limit on solvents (L1) having a HLB ofbetween 5 and 15 and a water solubility of >1.5 wt % at 20° C. of intotal less than 9 wt %, based on the total amount of solvents (L)present in the basecoat material, does the diffusion-governed swellingas a result of absorption of the specified solvents into thepolyurethane-polyurea particles present in the dispersion (PD), with anincrease in volume and with loss of their strength, not lead to unwantedeffects, especially rheological effects, as a result of which the highstorage stability with retention of good applications properties, statedas an objective, in aqueous basecoat materials can be achieved (seetables 3 and 4).

Solvents (L) here, in the sense of the invention and in agreement withthe knowledge of the skilled person in the paints sector (Römpp-LexikonLacke and Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,pages 358-359), are defined as liquid and volatile nonionic compoundswhich are present in the formulation at room temperature (i.e., 20° C.)under atmospheric pressure (i.e., 1.013 bar). The reference is thereforeto solvents which under baking conditions depart the resultant film toan extent of >10 wt %, preferably >25 wt %, and especiallypreferably >50 wt %. Baking conditions are understood at this point tomean the exposure of the respective coating material, followingapplication to a substrate, to a temperature of 140° C. for a durationof 20 minutes. This definition at any rate covers the volatile organicsolvents, and also water. An example of a solvent which is not a solvent(L1) in the sense of the invention, accordingly, isN,N-dimethylethanolamine.

It ought further to be noted that the at least one organic solvent (Z.2)and the solvents (L1) specified here by way of HLB values and watersolubility do not describe the same solvents. While solvents (Z.2) mayfall into the category of the solvents (L1) with a HLB of between 5 and15 and a water solubility >1.5 wt % at 20° C., they are selectedaccording to different criteria (see above).

Another advantage of the basecoat material of the invention is that itcan be prepared without the use of eco-unfriendly and health-injuriousorganic solvents such as N-methyl-2-pyrrolidone, dimethylformamide,dioxane, tetrahydrofuran, and N-ethyl-2-pyrrolidone. Accordingly, thebasecoat material preferably contains less than 10 wt %, preferably lessthan 5 wt %, more preferably less than 2.5 wt % of organic solventsselected from the group consisting of N-methyl-2-pyrrolidone,dimethylformamide, dioxane, tetrahydrofuran, and N-ethyl-2-pyrrolidone.The basecoat material is preferably entirely free from these organicsolvents.

The coating compositions of the invention can be produced using themixing assemblies and mixing techniques that are customary and known forthe production of basecoat materials.

The present invention likewise provides a method for producing multicoatpaint systems, in which

(1) an aqueous basecoat material is applied to a substrate,

(2) a polymer film is formed from the coating material applied in stage(1),

(3) a clearcoat material is applied to the resulting basecoat film, andthen

(4) the basecoat film is cured together with the clearcoat film,

which is characterized in that the aqueous basecoat material used instage (1) is a basecoat material of the invention.

All of the above remarks regarding the basecoat material of theinvention also apply to the method of the invention.

Said method is used to produce multicoat color paint systems, multicoateffect paint systems, and multicoat color and effect paint systems.

The aqueous basecoat material for use in accordance with the inventionis commonly applied to metallic or plastics substrates that have beenpretreated with a cured primer-surfacer. Said basecoat material mayoptionally also be applied directly to the plastics substrate or, in anintegrated process, directly to a metal substrate coated with anelectrocoat system.

Where a metallic substrate is to be coated, it is preferably furthercoated with an electrocoat system before the primer-surfacer is applied.

Where a plastics substrate is being coated, it is preferably alsopretreated before the primer-surfacer is applied. The techniques mostfrequently employed for such pretreatment are those of flaming, plasmatreatment, and corona discharge.

The pigmented aqueous basecoat material of the invention may be appliedto a metallic substrate, at the film thicknesses customary within theautomobile industry, in the range, for example, of 5 to 100 micrometers,preferably 5 to 60 micrometers. It is usual in this context to employspray application methods, such as compressed air spraying, airlessspraying, high-speed rotation, electrostatic spray application (ESTA),alone or in conjunction with hot spray application, such as hot airspraying, for example.

After the pigmented aqueous basecoat material has been applied, it canbe dried by known methods. For example, (1-component) basecoatmaterials, which are preferred, can be flashed at room temperature for 1to 60 minutes and subsequently dried, preferably at optionally slightlyelevated temperatures of 30 to 90° C. Flashing and drying in the contextof the present invention mean the evaporation of organic solvents and/orwater, as a result of which the paint becomes drier but has not yetcured or not yet formed a fully crosslinked coating film.

Then a commercial clearcoat material is applied, by likewise commonmethods, the film thicknesses again being within the customary ranges,for example 5 to 100 micrometers. Preference is given to two-componentclearcoat materials.

Following application of the clearcoat material, it may be flashed offat room temperature for 1 to 60 minutes, for example, and optionallydried. The clearcoat material is then cured together with the appliedbasecoat material. In the course of these procedures, crosslinkingreactions occur, for example, to produce on a substrate a multicoatcolor and/or effect paint system of the invention. The curing ispreferably effected by thermal means, at temperatures of 60 to 200° C.

All the film thicknesses stated in the context of the present inventionshould be understood as dry film thicknesses. The film thickness is thusthat of the cured film in question. Thus, if it is stated that a coatingmaterial is applied in a particular film thickness, this should beunderstood to mean that the coating material is applied such that thestated film thickness results after the curing.

Plastics substrates are coated basically in the same way as metallicsubstrates. However, curing is effected here generally at much lowertemperatures of to 90° C., in order not to cause any damage to and/ordeformation of the substrate.

The method of the invention can thus be used to paint metallic andnonmetallic substrates, more particularly plastics substrates,preferably automobile bodies or components thereof.

The method of the invention can be used further for dual finishing inOEM finishing. This means that a substrate which has been coated bymeans of the method of the invention is painted for a second time,likewise by means of the method of the invention.

The invention relates further to multicoat paint systems which areproducible by the method described above. These multicoat paint systemsare to be referred to below as multicoat paint systems of the invention.

All the above remarks relating to the aqueous basecoat material of theinvention and the method of the invention also apply correspondingly tosaid multicoat paint system.

A further aspect of the invention relates to the method of theinvention, wherein said substrate from stage (1) is a multicoat paintsystem having defects. This substrate/multicoat paint system havingdefects is thus an original finish, which is to be repaired (“spotrepair”) or completely recoated (“dual coating”).

The method of the invention is accordingly also suitable for repairingdefects on multicoat paint systems. Fault sites or film defects aregenerally faults on and in the coating, usually named according to theirshape or their appearance. The skilled person is aware of a host ofpossible kinds of such film defects.

The present invention further relates to the use of the basecoatmaterial of the invention comprising the specific solvent composition(L1) for improving the storage stability of basecoat materials whileretaining the good applications properties, more particularly the goodpinholing behavior, including in particular the reduction in thepinholing limit and number of pinholes, and also good running stability,on the part of the multicoat paint systems.

The invention is illustrated below using examples.

EXAMPLES

Methods of Determination

1. Solids Content

Unless otherwise indicated, the solids content, also referred to assolid fraction hereinafter, was determined in accordance with DIN EN ISO3251 at 130° C.; 60 min, initial mass 1.0 g. If reference is made in thecontext of the present invention to an official standard, this of coursemeans the version of the standard that was current on the filing date,or, if no current version exists at that date, then the last currentversion.

2. Isocyanate Content

The isocyanate content, also referred to below as NCO content, wasdetermined by adding an excess of a 2% strength N,N-dibutylaminesolution in xylene to a homogeneous solution of the samples inacetone/N-ethylpyrrolidone (1:1 vol %), by potentiometric back-titrationof the amine excess with 0.1 N hydrochloric acid, in a method based onDIN EN ISO 3251, DIN EN ISO 11909, and DIN EN ISO 14896. The NCO contentof the polymer, based on solids, can be calculated back via the fractionof a polymer (solids content) in solution.

3. Hydroxyl Number

The hydroxyl number was determined on the basis of R.-P. Kruger, R.Gnauck and R. Algeier, Plaste and Kautschuk, 20, 274 (1982), by means ofacetic anhydride in the presence of 4-dimethylaminopyridine as acatalyst in a tetrahydrofuran (THF)/dimethylformamide (DMF) solution atroom temperature, by fully hydrolyzing the excess of acetic anthydrideremaining after acetylation and conducting a potentiometricback-titration of the acetic acid with alcoholic potassium hydroxidesolution. Acetylation times of 60 minutes were sufficient in all casesto guarantee complete conversion.

4. Acid Number

The acid number was determined on the basis of DIN EN ISO 2114 inhomogeneous solution of tetrahydrofuran (THF)/water (9 parts by volumeof THF and 1 part by volume of distilled water) with ethanolic potassiumhydroxide solution.

5. Degree of Neutralization

The degree of neutralization of a component x was calculated from theamount of substance of the carboxylic acid groups present in thecomponent (determined via the acid number) and the amount of substanceof the neutralizing agent used.

6. Amine Equivalent Mass

The amine equivalent mass (solution) serves for determining the aminecontent of a solution, and was ascertained as follows. The sample foranalysis was dissolved at room temperature in glacial acetic acid andtitrated against 0.1N perchloric acid in glacial acetic acid in thepresence of crystal violet. The initial mass of the sample and theconsumption of perchloric acid gave the amine equivalent mass(solution), the mass of the solution of the basic amine that is neededto neutralize one mole of perchloric acid.

7. Degree of Blocking of the Primary Amino Groups

The degree of blocking of the primary amino groups was determined bymeans of IR spectrometry using a Nexus FT IR spectrometer (from Nicolet)with the aid of an IR cell (d=25 mm, KBr window) at the absorptionmaximum at 3310 cm⁻¹ on the basis of concentration series of the aminesused and standardization to the absorption maximum at 1166 cm⁻¹(internal standard) at 25° C.

8. Solvent Content

The amount of an organic solvent in a mixture, as for example in anaqueous dispersion, was determined by means of gas chromatography(Agilent 7890A, 50 m silica capillary column with polyethylene glycolphase or 50 m silica capillary column with polydimethylsiloxane phase,helium carrier gas, 250° C. split injector, 40-220° C. oven temperature,flame ionization detector, 275° C. detector temperature, n-propyl glycolas internal standard).

9. Number-Average Molar Mass

The number-average molar mass (M_(n)) was determined, unless otherwiseindicated, by means of a vapor pressure osmometer 10.00 (from Knauer) onconcentration series in toluene at 50° C. with benzophenone ascalibration substance for the determination of the experimentalcalibration constant of the instrument used, by the method of E.Schröder, G. Müller, K. F. Arndt, “Leitfaden derPolymercharakterisierung” [Principles of polymer characterization],Akademie-Verlag, Berlin, pp. 47-54, 1982.

10. Average Particle Size

The average particle size (volume average) of the polyurethane-polyureaparticles present in the dispersions (PD) for use in accordance with theinvention was determined in the context of the present invention bymeans of light scattering. Employed specifically for the measurement wasphoton correlation spectroscopy (PCS).

A Malvern Nano S90 (from Malvern Instruments) was used at 25±1° C. Theinstrument covers a size range from 3 to 3000 nm and was equipped with a4 mW He—Ne laser at 633 nm. The dispersions (PD) were diluted withparticle-free, deionized water as dispersing medium, before beingsubjected to measurement in a 1 ml polystyrene cell at suitablescattering intensity. Evaluation took place using a digital correlator,with the assistance of the Zetasizer analysis software, version 6.32(from Malvern Instruments). Measurement took place five times, and themeasurements were repeated on a second, freshly prepared sample. Thestandard deviation of a 5-fold determination was ≤4%. The maximumdeviation of the arithmetic mean of the volume average (V-average mean)of five individual measurements was ±15%. The reported average particlesize (volume average) is the arithmetic mean of the average particlesize (volume average) of the individual preparations. Verification wascarried out using polystyrene standards having certified particle sizesbetween 50 to 3000 nm.

11. Gel Fraction

The gel fraction of the polyurethane-polyurea particles (microgelparticles) present in the dispersions (PD) for use in accordance withthe invention is determined gravimetrically in the context of thepresent invention. Here, first of all, the polymer present was isolatedfrom a sample of an aqueous dispersion (PD) (initial mass 1.0 g) byfreeze-drying. Following determination of the solidificationtemperature—the temperature after which the electrical resistance of thesample shows no further change when the temperature is loweredfurther—the fully frozen sample underwent its main drying, customarilyin the drying vacuum pressure range between 5 mbar and 0.05 mbar, at adrying temperature lower by 10° C. than the solidification temperature.By graduated increase in the temperature of the heated surfaces beneaththe polymer to 25° C., rapid freeze-drying of the polymers was achieved;after a drying time of typically 12 hours, the amount of isolatedpolymer (solid fraction, determined by the freeze-drying) was constantand no longer underwent any change even on prolonged freeze-drying.Subsequent drying at a temperature of the surface beneath the polymer of30° C. with the ambient pressure reduced to maximum (typically between0.05 and 0.03 mbar) produced optimum drying of the polymer.

The isolated polymer was subsequently sintered in a forced air oven at130° C. for one minute and thereafter extracted for 24 hours at 25° C.in an excess of tetrahydrofuran (ratio of tetrahydrofuran to solidfraction=300:1). The insoluble fraction of the isolated polymer (gelfraction) was then separated off on a suitable frit, dried in a forcedair oven at 50° C. for 4 hours, and subsequently reweighed.

It was further ascertained that at the sintering temperature of 130° C.,with variation in the sintering times between one minute and twentyminutes, the gel fraction found for the microgel particles isindependent of sintering time. It can therefore be ruled out thatcrosslinking reactions subsequent to the isolation of the polymericsolid increase the gel fraction further.

The gel fraction determined in this way in accordance with the inventionis also called gel fraction (freeze-dried) and is stated in wt %. Thereason, evidently, is that it is the weight-based fraction of thepolyurethane-polyurea particles that has undergone crosslinking asdescribed at the beginning and can therefore be isolated as a gel.

In parallel, a gel fraction, hereinafter also called gel fraction (130°C.), was determined gravimetrically, by isolating a polymer sample fromaqueous dispersion (initial mass 1.0 g) at 130° C. for 60 minutes(solids content). The mass of the polymer was ascertained, after whichthe polymer was extracted in an excess of tetrahydrofuran at 25° C., inanalogy to the procedure described above, for 24 hours, after which theinsoluble fraction (gel fraction) was separated off, dried, andreweighed.

12. Solubility in Water

The solubility of an organic solvent in water was determined at 20° C.as follows. The respective organic solvent and water were combined in asuitable glass vessel, mixed, and the mixture was subsequentlyequilibrated. The amounts of water and of the solvent were selected suchthat two phases separate from one another were obtained after theequilibration. After the equilibration, a sample is taken from theaqueous phase (that is, the phase containing more water than organicsolvent) using a syringe, and this sample was diluted withtetrahydrofuran in a 1/10 ratio, the fraction of the solvent beingdetermined by means of gas chromatography (for conditions see section 8.Solvent content).

If two phases do not form irrespective of the amounts of water and thesolvent, the solvent is miscible with water in any weight ratio. Thissolvent that is therefore infinitely soluble in water (acetone, forexample) is therefore at any rate not a solvent (Z.2). The definition ofthe solvents (Z.2) is described earlier on above in the text.

Preparation of a Polyurethane-Polyurea Microgel (or aPolyurethane-Polyurea Dispersion (PD))

Example D1

Preparation of a Microgel for Use in Accordance with the Invention of aPolyesterurethaneurea by Addition of Diethylenetriaminediketimine to theExcess of a Partly Neutralized, m-Tetramethylxylene Diisocyanate-BasedPolyurethane Prepolymer in Methyl Ethyl Ketone and SubsequentCrosslinking Via Terminal Primary Amino Groups Following Dispersion inWater.

A microgel dispersion of a polyesterurethaneurea was prepared asfollows:

a) Preparation of a Partly Neutralized Prepolymer Solution

In a reaction vessel equipped with stirrer, internal thermometer, refluxcondenser, and electrical heating, 570.0 parts by weight of a linearpolyester polyol and 27.7 parts by weight of dimethylolpropionic acid(from GEO Speciality Chemicals) were dissolved under nitrogen in 344.4parts by weight of methyl ethyl ketone. The linear polyester diol wasprepared beforehand from dimerized fatty acid (Pripol® 1012, fromCroda), isophthalic acid (from BP Chemicals), and hexane-1,6-diol (fromBASF SE) (weight ratio of the starting materials: dimeric fatty acid toisophthalic acid to hexane-1,6-diol=54.00:30.02:15.98), and had ahydroxyl number of 73 mg KOH/g solid fraction, an acid number of 3.5 mgKOH/g solid fraction, a calculated number-average molar mass of 1379g/mol, and a number-average molar mass as determined via vapor pressureosmometry of 1350 g/mol.

Added to the resulting solution at 30° C. in succession were 202.0 partsby weight of m-tetramethylxylene diisocyanate (TMXDI® (Meta) aliphaticisocyanate, from Cytec), with an isocyanate content of 34.40 wt %, and3.8 parts by weight of dibutyltin dilaurate (from Merck). This wasfollowed by heating to 80° C. with stirring. Stirring was continued atthis temperature until the isocyanate content of the solution wasconstant at 1.51 wt %. Thereafter 626.4 parts by weight of methyl ethylketone were added to the prepolymer and the reaction mixture was cooledto 40° C. When 40° C. had been reached, 12.0 parts by weight oftriethylamine (from BASF SE) were added dropwise over the course of twominutes and the batch was stirred for a further 5 minutes.

b) Reaction of the Prepolymer with Diethylenetriaminediketimine

Then 30.8 parts by weight of a 71.9 wt % dilution ofdiethylenetriaminediketimine in methyl isobutyl ketone were mixed inover the course of one minute (ratio of prepolymer isocyanate groups todiethylenetriaminediketimine (having a secondary amino group): 5:1mol/mol, corresponding to two NCO groups per blocked primary aminogroup), and the reaction temperature rose by 1° C. briefly followingaddition to the prepolymer solution. The dilution ofdiethylenetriaminediketimine in methyl isobutyl ketone was preparedbeforehand by azeotropic removal of water of reaction in the reaction ofdiethylenetriamine (from BASF SE) with methyl isobutyl ketone in methylisobutyl ketone at 110-140° C. Adjustment to an amine equivalent mass(solution) of 124.0 g/eq was carried out by dilution with methylisobutyl ketone. Blocking of the primary amino groups of 98.5% wasdetermined by means of IR spectroscopy, on the basis of the residualabsorption at 3310 cm⁻¹.

The solids content of the polymer solution containing isocyanate groupswas found to be 45.0%.

c) Dispersion and Vacuum Distillation

After 30 minutes of stirring at 40° C., the contents of the reactor weredispersed in 1206 parts by weight of deionized water (23° C.) over thecourse of 7 minutes. Methyl ethyl ketone was distilled off from theresulting dispersion under reduced pressure at 45° C., and any losses ofsolvent and of water were made up with deionized water, giving a solidscontent of 40 wt %.

A white, stable, solids-rich, low-viscosity dispersion with crosslinkedparticles was obtained, and showed no sedimentation at all even after 3months.

The characteristics of the resulting microgel dispersion were asfollows:

Solids content (130° C., 60 min, 1 g): 39.6 wt %

Methyl ethyl ketone content (GC): 0.3 wt %

Methyl isobutyl ketone content (GC): 0.1 wt %

Viscosity (23° C., rotary viscometer, shear rate=1000/s): 15 mPa·s

Acid number 17.1 mg KOH/g

-   -   Solids content

Degree of neutralization (calculated) 49%

pH (23° C.) 7.4

Particle size (photon correlation spectroscopy, volume average) 156 nm

Gel fraction (freeze-dried) 83.3 wt %

Gel fraction (130° C.) 83.7 wt %

Comparative Example VD1

Preparation of a Dispersion of a Polyesterurethane Containing NoCrosslinked Particles by Dispersion of a Methyl Ethyl Ketone Solution ofa Partly Neutralized, Dicyclohexylmethane 4,4′-Diisocyanate-BasedPolyesterurethane

A standard polyurethane dispersion VD1 was prepared on the basis ofdicyclohexylmethane 4,4′-diisocyanate in accordance with WO 92/15405,page 15, lines 16-20.

The characteristics of the resulting polyurethane dispersion were asfollows:

Solids content (130° C., 60 min, 1 g): 27.0 wt %

Methyl ethyl ketone content (GC): 0.2 wt %

Viscosity (23° C., rotary viscometer, shear rate=1000/s): 135 mPa·s

Acid number 19.9 mg KOH/g

-   -   Solids content

pH (23° C.) 7.8

Particle size (photon correlation spectroscopy, volume average) 46 nm

Gel fraction (freeze-dried) −0.7 wt %

Gel fraction (130° C.) −0.3 wt %

Preparation of Waterborne Basecoat Materials

For the application comparison, a standard waterborne basecoat materialBL-V1 with the polyurethane dispersion VD1, containing no crosslinkedparticles, was prepared (according to WO 92/15405, page 15, lines16-20). In contrast to all inventive waterborne basecoat materials andthe further comparative waterborne basecoat materials, BL-V1 includes aphyllosilicate thickener, in order to prevent the vertical running fromthe metal panel during application and drying.

Phyllosilicate-free comparative waterborne basecoat materials BL-V2 toBL-V6 were prepared for comparison purposes on the basis of thedispersion (PD) D1 for inventive use, thus comprising crosslinkedparticles. Based on the total amount of solvents (L) present in thebasecoat material, all of the comparative waterborne basecoat materialscontain in total more than 9 wt % of solvents selected from the groupconsisting of solvents (L1) having a HLB of between 5 and 15 and a watersolubility of >1.5 wt % at 20° C. BL-V2 to BL-V6 are therefore notinventive waterborne basecoat materials.

Inventive waterborne basecoat materials BL-E1 to BL-E9 were prepared onthe basis of the dispersion (PD) D1, which in contrast to thecomparative waterborne basecoat materials BL-V2 to BL-V6, based on thetotal amount of solvents (L) present in the basecoat material, contain atotal of less than 9 wt % of solvents selected from the group consistingof solvents (L1) having a HLB of between 5 and 15 and a water solubilityof >1.5 wt % at 20° C.

The preparation of the waterborne basecoat materials is described indetail hereinafter.

Preparation of a Silver-Blue Waterborne Basecoat Material BL-V1 asComparative Example, Based on a Polyurethane Dispersion VD1 withPolyurethane Particles which are not Crosslinked, and Amenable to DirectApplication as a Coloring Coat onto a Cured Surfacer, Directly onto aPlastics Substrate or Directly onto a Metal Substrate Coated with anElectrocoat System

The components listed under “aqueous phase” in Table 1 are stirredtogether in the prescribed order to form an aqueous mixture. In the nextstep, an organic mixture is prepared from the components listed under“organic phase”. The organic mixture is added to the aqueous mixture.The combined mixture is then stirred for 10 minutes and adjusted, usingdeionized water and N,N-dimethylethanolamine (from BASF SE), to a pH of8.1 and to a high-shear viscosity of 58 mPa·s under a shearing load of1000 s⁻¹, as measured with a rotary viscometer (Rheomat RM 180instrument from Mettler-Toledo) at 23° C. This gave a solids content of17.6 wt %. The HLB values and corresponding water solubilities belongingto the solvent (L1) used have already been specified earlier on above inthe description.

TABLE 1 Preparation of a silver-blue waterborne basecoat material BL-V1Designation of the waterborne basecoat material BL-V1 Component Parts byweight AQUEOUS PHASE Aqueous solution of 3% sodium lithium 24.7magnesium phyllosilicate Laponite ® RD (from Altana-Byk) and 3%Pluriol ® P900 (from BASF SE) VD-1 Polyurethane dispersion, prepared 18according to page 15, Lines 16-20 of WO 92/15405 Hydroxy-functionalpolyester; prepared as per 3.2 example D, column 16, lines 37-59 ofDE-A-4009858 Luwipal ® 052 (from BASF SE), melamine- 4.3 formaldehyderesin TMDD 50% BG (from BASF SE), 52% strength 1.9 solution of2,4,7,9-tetramethyl-5-decyne-4,7- diol in butyl glycol 10% strengthsolution of N,N-dimethyl- 0.8 ethanolamine (from BASF SE) in water Butylglycol (from BASF SE) 5.7 Hydroxy-functional, polyurethane-modified 4.7polyacrylate; prepared as per page 7, line 55 to page 8, line 23 of DE4437535 A1 10 wt % strength solution of Rheovis ® AS 1130 4 (BASF SE),rheological agent 50 wt % strength solution of Rheovis ® PU 1250 0.47(BASF SE), rheological agent Isopropanol (from BASF SE) 1.9 Triethyleneglycol (from BASF SE) 2.4 2-Ethylhexanol (from BASF SE) 2 Isopar ® L(from ExxonMobil Chemical), solvent 1 (isoparaffinic hydrocarbon) Carbonblack paste 4.3 Blue paste 6.9 Red paste 0.23 Interference pigmentslurry Iriodin ® 9119 Polarweiß SW (from Merck), a 1 silver-whiteinterference pigment; mica, coated with rutile (TiO₂) Iriodin ® 9225 SQBRutil Perlblau SW (from 0.06 Merck), a blue interference pigment; mica,coated with rutile (TiO₂) Mixing varnish, prepared as per column 11, 3.2lines 1-17 of EP 1534792 - B1 Deionized water 7.98 ORGANIC PHASE Mixtureof two commercial aluminum pigments 0.36 STAPA Hydrolux 1071 aluminumand STAPA Hydrolux VP No. 56450/G aluminum (from Eckart Effect Pigments)Butyl glycol (from BASF SE) 0.5 Hydroxy-functional polyester; preparedas per 0.3 example D, column 16, lines 37-59 of DE-A- 4009858 10%strength solution of N,N-dimethyl- 0.1 ethanolamine (from BASF SE) inwater (for the adjustment of pH and spray viscosity)

Preparation of Inventive Waterborne Basecoat Materials (BL-E1 to BL-E6)Comprising the Polyurethaneurea Microgel D1 and, Based on the TotalAmount of Solvents (L) Present in the Basecoat Material, a Total of Lessthan 9 wt % of Solvents Selected from the Solvents (L1) with a HLB ofBetween 5 and 15 and a Water Solubility of >1.5 wt % at 20° C., and Alsoof Comparative Waterborne Basecoat Materials (BL-V2 to BL-V6) Comprisingthe Polyurethaneurea Microgel D1 and, Based on the Total Amount ofSolvents (L) Present in the Basecoat Material, a Total of More than 9 wt% of Solvents Selected from the Solvents (L1) with a HLB of Between 5and 15 and a Water Solubility of >1.5 wt % at 20° C., which can beApplied Directly as a Coloring Film to a Cured Surface, Directly to aPlastics Substrate, or Directly to a Metal Substrate Coated with anElectrocoat System.

The components listed under “aqueous phase” in table 2a and 2b arestirred together in the prescribed order to form an aqueous mixture. Inthe next step, an organic mixture is prepared from the components listedunder “organic phase”. The organic mixture is added to the aqueousmixture. The combined mixture is then stirred for 10 minutes andadjusted, using deionized water and N,N-dimethylethanolamine (from BASFSE), to a pH of 8 and to a high-shear viscosity of 58 mPas under ashearing load of 1000 s⁻¹, as measured with a rotary viscometer (RheomatRM 180 instrument from Mettler-Toledo) at 23° C.

TABLE 2a Preparation of comparative waterborne basecoat materials BL-V2to BL-V6. Designation of the waterborne basecoat material BL-V2 BL-V3BL-V4 BL-V5 BL-V6 Component: Parts by weight AQUEOUS PHASE Deionizedwater 18.6 18.6 18.6 18.6 18.6 Hydroxy-functional polyester; 5.8 5.8 5.85.8 5.8 prepared as per example D, column 16, lines 37-59 of DE 4009858A1 Luwipal ® 052 (from BASF SE), 7.8 7.8 7.8 7.8 7.8melamine-formaldehyde resin Butyl glycol (from BASF SE) 5.4 10.8Isobutanol 10.8 Butyl diglycol 10.8 Isopropanol 10.8 TMDD (from BASF SE)2 2 2 2 2 10% strength solution of N,N- 0.5 0.5 0.5 0.5 0.5dimethylethanolamine (from BASF SE) in water Hydroxy-functional,polyurethane- 8.5 8.5 8.5 8.5 8.5 modified polyacrylate; prepared as perpage 7, line 55 to page 8, line 23 of DE 4437535 A1 50 wt % strengthsolution of 0.8 0.8 0.8 0.8 0.8 Rheovis ® PU 1250 (from BASF SE) inwater, rheological agent PU microgel dispersion as per 20 20 20 20 20preparation example D1 Carbon black paste 7.8 7.8 7.8 7.8 7.8 Blue paste12.5 12.5 12.5 12.5 12.5 Red paste 0.4 0.4 0.4 0.4 0.4 Mica slurry asper EP 1534792 B1 - 7.7 7.7 7.7 7.7 7.7 column 11, lines 1-17 ORGANICPHASE: Aluminum pigment, available from 0.7 0.7 0. 0.7 0.7 Altana-Eckart2-Ethylhexanol 0.9 0.9 0.9 0.9 0.9 Hydroxy-functional polyester; 0.5 0.50.5 0.5 0.5 prepared as per example D, column 16, lines 37-59 of DE4009858 A1 10% strength solution of N,N- 0.1 0.1 0.1 0.1 0.1dimethylethanolamine (from BASF SE) in water (for the adjustment of pHand spray viscosity)

TABLE 2b Preparation of inventive waterborne basecoat materials BL-E1 toBL-E6. Designation of the waterborne basecoat material BL-E1 BL-E2 BL-E3BL-E4 BL-E5 BL-E6 Component: Parts by weight AQUEOUS PHASE Deionizedwater 18.6 18.6 18.6 18.6 19.8 19.8 Hydroxy-functional polyester; 5.85.8 5.8 5.8 prepared as per example D, column 16, lines 37-59 of DE4009858 A1 Hydroxy-functional polyester; 3.48 3.48 prepared as perexample BI1, page 8, paragraph 146 of US 2014/0065428 A1 Luwipal ® 0527.8 7.8 7.8 7.8 7.8 (from BASF SE), Melamine-formaldehyde resin Cymel ®385 (from Cytec), 7.64 Melamine-formaldehyde resin 2-Ethylhexanol 10.811.96 11.96 Diisobutyl ketone 10.8 Isopar ® L 10.8 Triethylene glycol10.8 TMDD (from BASF SE) 2 2 2 2 2 2 10% strength solution of 0.5 0.50.5 0.5 0.5 0.5 N,N-dimethylethanolamine (from BASF SE) in waterHydroxy-functional, 8.5 8.5 8.5 8.5 8.5 8.5 polyurethane-modifiedpolyacrylat; prepared as per page 7, line 55 to page 8, line 23 of DE4437535 A1 50 wt % strength solution 0.8 0.8 0.8 0.8 0.8 0.8 ofRheovis ® PU 1250 (from BASF SE) in water, rheological agent PU microgeldispersion as 20 20 20 20 20 20 per preparation example D1 Carbon blackpaste 7.8 7.8 7.8 7.8 7.8 7.8 Blue paste 12.5 12.5 12.5 12.5 12.5 12.5Red paste 0.4 0.4 0.4 0.4 0.4 0.4 Mica slurry as 7.7 7.7 7.7 7.7 7.7 7.7per EP 1534792 B1-column 11, lines 1-17 ORGANIC PHASE: Aluminum 0.7 0.70.7 0.7 0.7 0.7 pigment, available from Altana-Eckart 2-Ethylhexanol 0.90.9 0.9 0.9 0.9 0.9 Hydroxy-functional 0.5 0.5 0.5 0.5 0.5 0.5polyester; prepared as per example D, column 16, lines 37-59 of DE4009858 A1 10% strength solution of 0.1 0.1 0.1 0.1 0.1 0.1N,N-dimethylethanolamine (from BASF SE) in water (for the adjustment ofpH and spray viscosity)

Production of the Carbon Black Paste:

The carbon black paste was produced from 25 parts by weight of anacrylated polyurethane dispersion prepared as per international patentapplication WO 91/15528 binder dispersion A, 10 parts by weight ofcarbon black, 0.1 part by weight of methyl isobutyl ketone, 1.36 partsby weight of dimethylethanolamine (10% strength in DI water), 2 parts byweight of a commercial polyether (Pluriol® P900 from BASF SE), and 61.45parts by weight of deionized water.

Production of the Red Paste

The red paste was produced from 40 parts by weight of an acrylatedpolyurethane dispersion prepared as per international patent applicationWO 91/15528 binder dispersion A, 34.5 parts by weight of Cinilex® DPPRed, 2 parts by weight of a commercial polyether (Pluriol® P900 fromBASF SE), 3 parts by weight of 1-propoxy-2-propanol and 20.5 parts byweight of deionized water.

Production of the Blue Paste

The blue paste was produced from 69.8 parts by weight of an acrylatedpolyurethane dispersion prepared as per international patent applicationWO 91/15528 binder dispersion A, 12.5 parts by weight of Paliogen® BlueL 6482, 1.5 parts by weight of dimethylethanolamine (10% strength in DIwater), 1.2 parts by weight of a commercial polyether (Pluriol® P900from BASF SE), and 15 parts by weight of deionized water.

Comparative Experiments Between the Inventive Waterborne BasecoatMaterials BL-E1 to BL-E6 with the Waterborne Basecoat Materials BL-V1 toBL-V2 in Respect of the Running Limit, Popping Limit, and PinholingLimit, and Number of Pinholes.

For the determination of the applications properties (running limit,popping limit, and pinholing limit and the number of pinholes),multicoat paint systems were produced using the waterborne basecoatmaterials (BL-V1 to BL-V2 and also BL-E1 to BL-E6) according to thefollowing general protocol:

A steel panel of dimensions 30 cm×50 cm coated with a cured surfacersystem was provided with an adhesive strip on one longitudinal edge, inorder to be able to determine the film thickness differences aftercoating. The waterborne basecoat material was applied electrostaticallyin wedge format. The resulting waterborne basecoat film was flashed offat room temperature for one minute and subsequently dried in an aircirculation oven at 70° C. for 10 minutes. Applied atop the driedwaterborne basecoat film was a ProGloss® two-component clearcoatmaterial available commercially from BASF Coatings GmbH. The resultingclearcoat film was flashed off at room temperature for 20 minutes.Waterborne basecoat film and clearcoat film were then jointly cured inan air circulation oven at 140° C. for 20 minutes. The film thickness ofthe cured clearcoat film was constant over the whole panel (±1 μm), witha clearcoat film thickness of 35 to 45 μm.

In the case of the determination of the popping limit, pinholing limitand number of pinholes, the panels were dried horizontally in an aircirculation oven and cured, and the popping limit and pinholing limitwere determined visually, by ascertaining the resulting film thicknessof the basecoat film, increasing in wedge format, at which pops andpinholes, respectively, first occurred. In the case of the number ofpinholes, furthermore, a determination was made of the number ofpinholes which occurred on the coated metal panel with the edge length30 cm×50 cm.

In the case of the determination of the running limit, perforated metalpanels with the same dimensions, made from steel, were used; the panelswere coated as described above, and the applied coating materials weredried and cured as described above, except that the panels were placedvertically in the oven in each case after application of waterbornebasecoat material and application of clearcoat material.

The film thickness from which runs occur is termed the running limit,and was ascertained visually.

Table 3 provides an overview of the results of the determination ofrunning limit, popping limit, and pinholing limit, and also number ofpinholes:

Whereas waterborne basecoat material BL-V1 had no crosslinked particlesand contained a Laponite® RD phyllosilicate thickener, all of the otherwaterborne basecoat materials were free from this thickener componentand contained the crosslinked polyurethane-urea dispersion D1 forinventive use.

While the comparative waterborne basecoat materials BL-V1 and BL-V2,based on the total amount of solvents (L) present in the basecoatmaterial, contained in total more than 9 wt % of solvents selected fromthe group consisting of solvents (L1) having a HLB of between 5 and 15and a water solubility of >1.5 wt % at 20° C., the inventively preparedwaterborne basecoat materials BL-E1 to BL-E6, based on the total amountof solvents (L) present in the basecoat material, contain in total lessthan 9 wt % of solvents selected from the group consisting of solvents(L1) having a HLB of between 5 and 15 and a water solubility of >1.5 wt% at 20° C.

TABLE 3 Results of the determination of running limit, popping limit,and pinholing limit, and also number of pinholes, for multicoat paintsystems based on the waterborne basecoat materials BL-V1 to BL-V4 andBL-E1 to BL-E6 Designation of the waterborne basecoat material BL-V1BL-V2 BL-E1 BL-E2 BL-E3 BL-E4 BL-E5 BL-E6 Polyurethane VD1 D1 D1 D1 D1D1 D1 D1 dispersion Contains Yes No No No No No No No Laponite ® RDthickener solution¹⁾ Amount in wt %, >9 17.60 8.52 8.52 8.52 8.52 6.864.41 based on the total amount of solvents (L) present in the basecoatmaterial, of solvents (L1) with an HLB of between 5 and 15 and a watersolubility >1.5 wt % at 20° C. Running limit23 >60 >60 >60 >60 >60 >60 >60 in μm²⁾ Popping limit 12 31 34 37 35 3239 38 in μm³⁾ Pinholing limit 16 30 31 33 31 34 35 37 in μm³⁾ Number of17 20 17 25 21 22 12 14 pinholes⁵⁾ ¹⁾Laponite ® RD thickener solution:Aqueous solution of 3% sodium lithium magnesium phyllosilicateLaponite ® RD (from Altana-Byk) and 3% Pluriol ® P900 (from BASF SE)²⁾Running limit in μm: Film thickness from which runs occur ³⁾Poppinglimit in μm: Film thickness from which runs occur ⁴⁾Pinholing limit inμm: Film thickness of the basecoat film from which pinholes occurfollowing application of a wedge of basecoat material and a constantlayer of a two-component clearcoat material, with joint curing in an aircirculation oven at 140° C., 20 minutes ⁵⁾Number of pinholes: Number ofpinholes from pinholing limit of the coated metal panel with edge length30 cm × 50 cm

The results of table 3 show that the use of the dispersion (PD) D1 foruse in accordance with the invention in the waterborne basecoatmaterials BL-E1 to BL-E6 and also BL-V2 exhibits distinct advantages inrespect of all the applications properties evaluated. Furthermore, it isclearly apparent in comparison to BL-V2 that the inventivespecifications concerning the solvents (L1) used in the inventivewaterborne basecoat materials BL-E1 to BL-E6 do not lead to any adverseeffects on the applications properties. Instead, a further reduction inthe fraction of the solvents (L1) having a HLB of between 5 and 15 and awater solubility of >1.5 wt % at 20° C., based on the total amount ofsolvents (L) present in the basecoat material, to below 7 wt % (BL-E5)and below 5 wt % (BL-E6) leads to a still further-improved pinholingbehavior, as evidenced by the increased pinholing limit.

Comparison Between the Inventive Waterborne Basecoat Materials BL-E1 toBL-E6 with the Comparative Waterborne Basecoat Materials BL-V1 to BL-V6in Relation to Solids Content and Viscosity

As well as improved or at least the retention of good applicationsproperties, the waterborne basecoat materials prepared in accordancewith the invention ought likewise to exhibit good storage stabilities.

The storage stability of the inventively prepared waterborne basecoatmaterials BL-E1 to BL-E6 was investigated on the basis of the high-shearviscosity over a period of 20 days and was contrasted with the standardwaterborne basecoat material BL-V1, which contained a phyllosilicatethickener and the noncrosslinked microgel dispersion VD1.

As a second comparator, the waterborne basecoat materials BL-V2 toBL-V6, comprising the polyurethane-urea dispersion D1, were employed,which were likewise free of phyllosilicate thickeners but likecomparative waterborne basecoat material BL-V1, and in contrast to theinventive waterborne basecoat materials BL-E1 to BL-E6, based on thetotal amount of solvents (L) present in the basecoat material, containedin total more than 9 wt % of solvents selected from the group ofsolvents (L1) having a HLB of between 5 and 15 and a water solubilityof >1.5 wt % at 20° C.

The high-shear viscosity was measured at a shear rate of 1000 l/s,measured using a rotary viscometer (Rheomat RM 180 instrument fromMettler-Toledo) at 23° C., within one hour after the preparation of therespective waterborne basecoat material, and also after 2, 4, 8, and 20days. Apart from the respective measurements, the samples were storedover the entire period at 23° C. without influence of external shearingforces, and were shaken for one minute a short time prior tomeasurement.

The results are set out in table 4a and 4b.

TABLE 4a Characterization of the comparative waterborne basecoatmaterials BL-V1 to BL-V6 in relation to solids content and viscosityDesignation of the waterborne basecoat material BL-V1 BL-V2 BL-V3 BL-V4BL-V5 BL-V6 Polyurethane dispersion VD1 D1 D1 D1 D1 D1 ContainsLaponite ® Yes No No No No No RD thickener solution¹⁾ Amount in wt %,based >9 17.6 24.0 24.0 24.0 24.0 on the total amount of solvents (L)present in the basecoat material, of solvent (L1) with HLB of between 5and 15 and a water solubility >1.5 wt % at 20° C. Solids content 17.629.1 28.3 29.3 27.5 29.7 High-shear viscosity in mPa · s at 1000s⁻¹after 0 days 58 62 62 65 61 64 2 days 59 68 72 84 85 87 4 days 62 74 78106 81 93 8 days 60 77 81 94 84 94 20 days 59 78 81 114 99 166¹⁾Laponite ® RD thickener solution: Aqueous solution of 3% sodiumlithium magnesium phyllosilicate Laponite ® RD (from Altana-Byk) and 3%Pluriol ® P900 (from BASF SE)

TABLE 4b Characterization of the inventive waterborne basecoat materialsBL-E1 to BL-E6 in relation to solids content and viscosity Designationof the waterborne basecoat material BL-E1 BL-E2 BL-E3 BL-E4 BL-E5 BL-E6Polyurethane dispersion D1 D1 D1 D1 D1 D1 Contains Laponite ® No No NoNo No No RD thickener solution ¹⁾ Amount in wt %, based on the 8.5 8.58.5 8.5 6.9 4.4 total amount of solvents (L) present in the basecoatmaterial, of solvent (L1) with HLB of between 5 and 15 and a watersolubility >1.5 wt % at 20° C. Solids content 30.1 30.7 31.1 32.5 33.734.1 High-shear viscosity in mPa · s at 1000s⁻¹ after 0 days 63 67 67 6664 67 2 days 70 64 69 71 66 69 4 days 73 65 70 72 67 69 8 days 73 63 6865 66 68 20 days 69 58 65 64 66 68

The results in table 4a and 4b show that the inventive basecoatmaterials exhibit excellent storage stability for a solids content inthe range from 30 to 35 wt %. The high-shear viscosity of the inventivebasecoat materials BL-E1 to BL-E6 remains virtually unchanged over aperiod of 20 days and therefore satisfies the requirements, whereas thenoninventive, comparative basecoat materials BL-V2 to BL-V6 do notsatisfy these rheology stability requirements. They exhibit a markedrise in the high-shear viscosity.

The environmentally advantageous further reduction in the fraction ofthe solvent content (L1) with an HLB of between 5 and 15 and a watersolubility of >1.5 wt % at 20° C. among the sum total of the solvents(L) in an aqueous basecoat material, to below 7 wt % (BL-E5) and below 5wt % (BL-E6), therefore leads likewise to excellent storage stabilities.

The combination of a polyurethane dispersion VD1, with polyurethaneparticles which are not crosslinked, with phyllosilicate thickeners inthe comparative waterborne basecoat material BL-V1 likewise exhibitsstable high-shear viscosities in these tests, but the applicationsproperties shown above are significantly disadvantageous in relation tothe inventive variants.

Preparation of Inventive, Effect Pigment-Free Waterborne BasecoatMaterials Comprising the Polyurethaneurea Microgel D1 and, Based on theTotal Amount of Solvents (L) Present in the Basecoat Material, a Totalof Less than 9 wt % of Solvents Selected from the Group Consisting ofSolvents (L1) with a HLB of Between 5 and 15 and a Water Solubilityof >1.5 wt % at 20° C., with a High Solids Content in the Range from 45to 55 wt % (BL-E7 to BL-E9), which can be Applied Directly as a ColoringFilm to a Cured Surface, Directly to a Plastics Substrate, or Directlyto a Metal Substrate Coated with an Electrocoat System.

The inventive, effect pigment-free waterborne basecoat materials BL-E7to BL-E9 were prepared in analogy to the protocol for preparing thecomparative waterborne basecoat materials BL-V2 to BL-V6 and BL-E1 toBL-E6, using the components listed in table 5. With the aid of deionizedwater and N,N-dimethylethanolamine (from BASF SE), they were adjusted toa pH of 8 and a high-shear viscosity of 125 mPas under a shearing loadof 1000 s⁻¹, as measured with a rotary viscometer (Rheomat RM 180instrument from Mettler-Toledo) at 23° C.

TABLE 5 Preparation of inventive waterborne basecoat materials BL-E7 toBL-E9. Designation of the waterborne basecoat material BL- BL- BL- E7 E8E9 Component: Parts by weight AQUEOUS PHASE Deionized water 10 10.8 11Hydroxy-functional polyester; prepared as per 4.2 example D, column 16,lines 37-59 of DE 4009858 A1 Hydroxy-functional polyester; prepared asper 2.52 2.52 example BI1, page 8, paragraph 146 of US 2014/0065428 A1Luwipal ® 052 (from BASF SE), melamine- 5.8 5.8 formaldehyde resinCymel ® 385 (from Cytec), 5.68 melamine-formaldehyde resin2-Ethylhexanol, HLB 4.8 2.7 3.5 3.5 Triethylene glycol, HLB 20.0 2.7 2.72.7 10% strength solution of N,N-dimethylethanol- 0.5 0.5 0.5 amine(from BASF SE) in water Hydroxy-functional polyurethane modified 6.3 6.36.3 polyacrylate; prepared as per page 7, line 55 to page 8, line 23 ofDE 4437535 A1 50 wt % strength solution of Rheovis ® PU 1250 0.6 0.6 0.6(from BASF SE) in water, rheological agent PU microgel dispersion as perpreparation 16.4 16.4 16.4 example D1 Carbon black paste 0.1 0.1 0.1White paste 50.7 50.7 50.7

The preparation of the carbon black paste has already been describedunder table 2b.

Preparation of the White Paste:

The white paste was produced from 43 parts by weight of an acrylatedpolyurethane dispersion prepared as per international patent applicationWO 91/15528 binder dispersion A, 50 parts by weight of titanium rutile2310, 3 parts by weight of 1-propoxy-2-propanol and 4 parts by weight ofdeionized water.

Comparative Experiments Between the Inventive Waterborne BasecoatMaterials BL-E7 to BL-E9 in Respect of Run Stability and PoppingStability, Pinholing Limit, and Also Number of Pinholes and Viscosity.

For the determination of the applications properties (running limit,popping limit, and pinholing limit and the number of pinholes),multicoat paint systems were produced using the waterborne basecoatmaterials (BL-E7 to BL-E9) in analogy to the preceding protocol (seeprotocol of table 3).

The storage stability of the phyllosilicate-free, inventively preparedwaterborne basecoat materials BL-E7 to BL-E9 was investigated in analogyto the preceding protocol (protocol above table 4a) on the basis of thehigh-shear viscosity over a period of 20 days.

The results are set out in table 6.

TABLE 6 Results of the determination of running limit, popping limit,and pinholing limit, and also number of pinholes, for multicoat paintsystems and the viscosity based on the waterborne basecoat materialsBL-E7 to BL-E9. Designation of the waterborne basecoat material BL-E7BL-E8 BL-E9 Polyurethane dispersion D1 D1 D1 Amount in wt %, based onthe total amount 8.9 7.2 4.5 of solvents (L) present in the basecoatmaterial, of solvents (L1) with an HLB of between 5 and 15 and a watersolubility >1.5 wt % at 20° C. Solids content 47.6 51.5 52.4 Runninglimit in μm¹⁾ >70 >70 >70 Popping limit in μm²⁾ 47 49 46 Pinholing limitin μm³⁾ 44 48 42 Number of pinholes⁴ 6 13 8 High-shear viscosity in mPa· s at 1000 s¹ after  0 days 126 123 128  2 days 129 125 131  4 days 131124 133  8 days 133 126 129 20 days 134 122 128 ¹⁾Running limit in μm:Film thickness from which runs occur ²⁾Popping limit in μm, Filmthickness from which pops occur ³⁾Pinholing limit in μm: Film thicknessof the basecoat film from which pinholes occur following application ofa wedge of basecoat material and a constant layer of a two-componentclearcoat material, with joint curing in an air circulation oven at140°C., 20 minutes ⁴⁾Number of pinholes: Number of pinholes frompinholing limit of the coated metal panel with edge length 30 cm × 50 cm

-   1) Running limit in μm: Film thickness from which runs occur-   2) Popping limit in μm, Film thickness from which pops occur-   3) Pinholing limit in μm: Film thickness of the basecoat film from    which pinholes occur following application of a wedge of basecoat    material and a constant layer of a two-component clearcoat material,    with joint curing in an air circulation oven at 140° C., 20 minutes-   4) Number of pinholes: Number of pinholes from pinholing limit of    the coated metal panel with edge length 30 cm×50 cm

The results of table 6 demonstrate that the use of the dispersion D1 forinventive use in the waterborne basecoat materials BL-E7 to BL-E9, i.e.,the inventive waterborne basecoat materials with a high solids contentin the range from 47 to 53 wt %, leads to excellent applicationsproperties. The running, popping, and pinholing limits were raisedsignificantly further in comparison to the already good results of theinventive waterborne basecoat materials BL-E1 to BL-E6 (table 3), andthe number of pinholes was reduced further.

Moreover, the results of table 6 demonstrate that the inventive basecoatmaterials with a high solids fraction (BL-E7 to BL-E9) also achieveexcellent storage stability, as evidenced by a small change in thehigh-shear viscosity over a period of 20 days.

The further reduction in the fraction of the solvent content (L1) with aHLB between 5 and 15 and a water solubility of >1.5 wt % at 20° C. amongthe sum total of the solvents (L), to below 7.5 wt % (BL-E8) and below 5wt % (BL-E9), does not lead to any significant change in theinvestigated applications properties and storage stabilities incomparison to the inventive waterborne basecoat material BL-E7.

It has been shown, ultimately, that a significant improvement can beachieved in the applications properties and in the storage stability ofaqueous basecoat materials comprising color pigments, even with anenvironmentally more advantageous high solids content.

In summary the examples show that the inventive waterborne basecoatmaterials BL-E1 to BL-E9 combine very good applications properties withexcellent storage stability in relation to the comparative waterbornebasecoat materials BL-V1 to BL-V6. The standard waterborne basecoatmaterial BL-V1, which comprises a polyurethane dispersion VD1 withnoncrosslinked particles, does have a good stability of viscosity onstorage, but achieves markedly poorer applications properties. Thecomparative waterborne basecoat materials BL-V2 to BL-V6, which comprisethe microgel dispersion D1 for inventive use, do achieve goodapplications properties, but not satisfactory storage stabilities.

It is only the inventive waterborne basecoat materials, then, thatresolve the problem addressed by the present specification, namely anexcellent storage stability with accompanying retention of goodapplications properties.

1. A pigmented aqueous basecoat material comprising an aqueouspolyurethane-polyurea dispersion (PD) having polyurethane-polyureaparticles present in the dispersion, having an average particle size(volume average) of 40 to 2000 nm, and having a gel fraction of at least50 wt %, the polyurethane-polyurea particles, in each case in reactedform, comprising: (Z.1.1) at least one polyurethane prepolymercontaining isocyanate groups and comprising anionic groups and/or groupswhich can be converted into anionic groups, and (Z.1.2) at least onepolyamine comprising two primary amino groups and one or two secondaryamino groups, wherein the aqueous basecoat material, based on the totalamount of solvents (L) present in the basecoat material, contains intotal less than 9 wt % of solvents selected from the group consisting ofsolvents (L1) having a hydrophilic-lipophilic balance (HLB) of between 5and 15 and a water solubility of greater than 1.5 wt % at 20° C., theHLB of a solvent (L) being defined as:HLB(L)=20*(1−M(lipophilic fraction of (L))/M(L)), the lipophilicfraction of a solvent (L) being made up of the followingcarbon-containing groups: every group CH_(n) with n=1 to 3, providedthat the group: (i) is not in alpha position to OH, NH₂, CO₂H, (ii) isnot in ethylene oxide units located in an ethylene oxide chain having aterminal OH group, and/or (iii) is not in a cyclic molecule or molecularmoiety in alpha position to a bridging functional group selected from—O—, NH—.
 2. The pigmented aqueous basecoat material as claimed in claim1, wherein the prepolymer (Z.1.1) of the polyurethane-polyureadispersion comprises carboxylic acid groups.
 3. The pigmented aqueousbasecoat material as claimed in claim 1, wherein the dispersion (PD)consists, up to at least 90 wt %, of the polyurethane-polyurea particlesand water.
 4. The pigmented aqueous basecoat material as claimed inclaim 1, further comprising a melamine formaldehyde resin and at leastone hydroxy-functional polymer that is different from the polymerpresent in the dispersion (PD).
 5. The pigmented aqueous basecoatmaterial as claimed in claim 1, wherein, based on the total amount ofsolvents (L) present in the basecoat material, the basecoat materialcontains in total less than 9 wt % of solvents selected from the groupconsisting of solvents (L1) having a HLB of more than 7.8 and a watersolubility of more than 7.7 at 20° C.
 6. A pigmented aqueous basecoatmaterial comprising an aqueous polyurethane-polyurea dispersion (PD)having polyurethane-polyurea particles present in the dispersion, havingan average particle size (volume average) of 40 to 2000 nm, and having agel fraction of at least 50 wt %, the polyurethane-polyurea particles,in each case in reacted form, comprising: (Z.1.1) at least onepolyurethane prepolymer containing isocyanate groups and comprisinganionic groups and/or groups which can be converted into anionic groups,and (Z.1.2) at least one polyamine comprising two primary amino groupsand one or two secondary amino groups, wherein the aqueous basecoatmaterial, based on the total amount of solvents (L) present in thebasecoat material, contains in total less than 9 wt % of butyl glycol,butyl diglycol, isopropanol, n-propanol, 1-propoxy-2-propanol,isobutanol and/or n-butanol.
 7. A pigmented aqueous basecoat materialcomprising an aqueous polyurethane-polyurea dispersion (PD) havingpolyurethane-polyurea particles present in the dispersion, having anaverage particle size (volume average) of 40 to 2000 nm, and having agel fraction of at least 50 wt %, the polyurethane-polyurea particles,in each case in reacted form, comprising: (Z.1.1) at least onepolyurethane prepolymer containing isocyanate groups and comprisinganionic groups and/or groups which can be converted into anionic groups,and (Z.1.2) at least one polyamine comprising two primary amino groupsand one or two secondary amino groups, wherein the aqueous basecoatmaterial, based on the total amount of solvents (L) present in thebasecoat material, contains in total less than 9 wt % of butyl glycol.8. The pigmented aqueous basecoat material as claimed in claim 1 havinga solids content of 15 to 60 wt %.
 9. The pigmented aqueous basecoatmaterial as claimed in claim 1 having a viscosity of 40 to 180 mPa·s at23° C. under a shearing load of 1000 l/s.
 10. The pigmented aqueousbasecoat material as claimed in claim 1, wherein a percentage total ofthe solids content of the basecoat material and a fraction of water inthe basecoat material is at least 70 wt %.
 11. The pigmented aqueousbasecoat material as claimed in claim 10, wherein the percentage totalof the solids content of the basecoat material and the fraction of waterin the basecoat material is at least 80 wt %.
 12. A method of using apigmented aqueous basecoat material as claimed in claim 1, the methodcomprising applying the basecoat material as a basecoat film in amulticoat paint system to improve the storage stability and theapplications properties.
 13. A method for producing a multicoat paintsystem comprising the stages: (1) applying a pigmented aqueous basecoatmaterial to a substrate, (2) forming a polymer film from the coatingmaterial applied in stage (1), (3) applying a clearcoat material to theresulting basecoat film, and (4) curing the basecoat film together withthe clearcoat film, wherein the pigmented aqueous basecoat material asclaimed claim 1 is used in stage (1).
 14. The method as claimed in claim13, wherein the substrate is a metallic substrate coated with a curedelectrocoat film, and all of the films applied to the electrocoat filmare cured jointly.
 15. A multicoat paint system producible by the methodas claimed in claim
 13. 16. The pigmented aqueous basecoat material asclaimed in claim 8 having a solids content of 30 to 55 wt %.
 17. Thepigmented aqueous basecoat material as claimed in claim 9 having aviscosity of 60 to 135 mPa·s at 23° C. under a shearing load of 1000l/s.